I have VCA in Samplitude and have no use for it. I understand the ability to have a proportional control over many tracks but Sonar has that. Always has. There maybe some other feature they offer but its seem a bit obscure. 
 
Further leaving a DAW for a single feature that only recently became available seems silly. A threat that doesn't look like a threat but a relief to CW.  

Frequency Studios
 
 
Quickly though for one example groups as they exist currently in Sonar will not allow you to automate individual tracks inside the group without deselecting that track from the group...

If you hold the control key while moving a fader (or any control), it's grouping is temporarily suspended, allowing you to automate just that track. Once control key is released, it'll resume moving proportionally to the others, assuming you've set them up for relative movement. Does that achieve your goal?

What's also weird is that it sounds like the OP might be confusing Groups with Buses. Grouping channel faders together does not apply the same processing to the channels, which can still be routed to any bus (and now maybe aux tracks?) you want. I'll have to sit down to confirm this but the only thing they don't do which VCAs do is give you a dedicated track fader to represent the group. I wonder if you can create a dummy Aux track and add it to a group and have it be your VCA? I suspect there'd still be missing some slightly more elegant tools for managing them (like a dedicated track picker for example)
 
 

With DCAs you could have a particular fader/track/channel present in several groups.

In Sonar a fader can only be in any one group. I haven't tested this. It's not expressly mentioned in the manual whether a control element can be in only one or more than one.

It allows you to create sub mixes for monitoring groups against each other.

Setup a drums DCA group then setup a Rhythms DCA group. The Rhythm DCA includes all the elements in the Drums DCA as well as the Bass track. You could have a Bass DCA that includes the Kick drum and toms along with bass guitar. Now you have 3 DCA groups with some over lap of group membership.

mudgel
With DCAs you could have a particular fader/track/channel present in several groups.

In Sonar a fader can only be in any one group. I haven't tested this. It's not expressly mentioned in the manual whether a control element can be in only one or more than one.

It allows you to create sub mixes for monitoring groups against each other.

Setup a drums DCA group then setup a Rhythms DCA group. The Rhythm DCA includes all the elements in the Drums DCA as well as the Bass track. You could have a Bass DCA that includes the Kick drum and toms along with bass guitar. Now you have 3 DCA groups with some over lap of group membership.

Nice description of what they can add to the party, Mike.      Voted.
 
 

mudgel
With DCAs you could have a particular fader/track/channel present in several groups.

Ahhhhhh, right! Good reminder.

Hatstand
perhaps you could explain the scenarios where the current track automation grouping falls short of your
needs? it might help your fellow forum contributors understand what you think is missing in the current
functionality. The manual information is here;
https://www.cakewalk.com/...mp;help=Mixing.43.html

If doing any relative movement of a control like fader involving sends - then VCA may be useful.
The fader change which also include a change in return from sends should maintain the same sum of wet from returns and dry signal - or it will sound different.
 
Let's say we have reference level of 100 on fader and 50% of that amount, level 50 below fader through a send. Sum is 150 and wet is 1/3 of total.
 
Then lower fader to 90 and send is 45 and sum is 135 and wet is 1/3 of total - this is what we want.
 
What normal sends do is not percentage change but a fixed amount of fader - meaning lowering fader to 90 send becomes 40 - which is 50 below fader and does not sound the same 90+40=130 and wet is 40/130 and 30.8% instead of 33.3% and will sound different.
 
In theory you can do this in Sonar through grouping controls and percentage change - but involves a
calculation of separate percentage every relative change of fader automation. So in real life not very
practical. A VCA fader handles that for you.
 
Better way in Sonar would be to automate a bus fader and see to that any returns are into that bus as
well - then you can change level of bus fader and ratio wet&dry is the same. Through patch points you
can do this. But it gives less freedom than VCA grouping does.
 
Samplitude has VCA faders but they do not allow nested in many levels - so very limited.
ProTools and Cubase Pro allow nested VCA grouping.
 
Limitations of VCA grouping is always if sends involve any non-linear effects in chain - this cannot be
handled and result will sound different. This could be doing NY style parallell compression with a
compressor - and there VCA is not any help.
 
For me other things are top priority to move back from Cubase, but vote for VCA now will take a good while to implement - so voting.

Perhaps I have this wrong, but if you have a pre fade send from the main track to an aux track and group the two tracks would this not resolve the scenario above where moving one fader moves the other?
 
I guess different people have different preferred ways of working. I must admit I usually sum to busses and automate from there.

Is there a way one automation lane could control multiple volume faders in a VCA-like fashion? Lets say you wanted to have vocals, drums, etc. grouped together, so you could automate a complex mix, but have it to where the group "masters" (and their automation lanes) remote controlled the individual channel volumes, preserving their relationship to aux sends. I don't think busses work this way, do they?

In answer to the question posed in the post above.
From the page 1070 of the manual.
Using control groups
SONAR lets you link faders, knobs, or buttons in the Track view, Track Inspector and Console view into groups.
Groups are collections of controls whose movements are linked together. For example:
Two Volume faders or controls can be grouped so that when you increase or decrease the volume of one track,
the volume of the other track changes in exactly the same way.
Four Mute buttons can be grouped so that when you click on the Mute button to mute track 1, tracks 1 and 2
are muted and tracks 3 and 4 are un-muted.
The Console view and Track view identify controls, knobs and faders that are grouped using a colored group
indicator that is displayed on the controls in each group. The controls in group A are displayed with a red indicator,
the controls in group B with a green indicator, and so on. Controls, faders and knobs can be grouped together.
When you group buttons together, the way they work is based on their position when you create the group:
Buttons that are in the same position when grouped will turn on and off together at all times.
Buttons that are in opposite positions when grouped will always remain in opposite positions.
When you group buttons with knobs or faders, the button turns on/off when the knob or fader reaches its halfway
point.
You have several additional options. There are three general types of groups: absolute, relative, and custom.
Here’s how they work.
Absolute
The range of motion in all controls in the group is identical. When you move one control in the group, all other
controls in the group move the same amount in the same direction. The controls do not necessarily need to start at
the same level.
Relative
The range of motion for controls in the group is not the same. All controls in the group have the same value at one
point—the lowest level for send, return, and volume levels, and zero for pan controls.
Custom
Sometimes you want to define a more complex relationship between the controls in a group. For example:
You want two controls to operate in reverse—when one fader drops, the other increases (cross fade).
You want two volume faders grouped so that they are locked together at maximum level, but drop at different
rates.
You want two faders to be locked together with the same range of motion, but a third fader grouped with them
to have a different rang