I posted about this quite a while back (several months) and never really got a definite fix.  I haven't had a chance to work much with Sonar for a while because I've been finishing up on a huge video project that I have been working on.
 
Well, now that I've gotten back to working with SPlat...my reverb tail problem is still there.  I always create a sub group for...lets say lead vox.  I put the reverb plug (Breverb) on that bus.  This way, when I do a volume edit mute (or physically cut and remove the space) to mute out a "silent" space (maybe a cough) the reverb tail will continue until faded out....unlike if you have the reverb on the main vox track, where it will cut off as soon as you mute with volume control or a cut.
 
What I have found is...if I place the CA-2A comp on the bus, BEFORE the reverb, the verb tails cut off.  But if I place the CA=2A AFTER the reverb...the verb tail fades out like it should.
 
I know the work around is to either place the CA-2A on the main track instead of the bus (sometimes I place it on both main track AND bus)...or place it after the reverb plug.  But I have used this work flow for a long time with great success, until this bug showed up.
 
Maybe this is something the bakers would like to look into...see if they can reproduce it (or any of you for that matter)  :) .  Then again, maybe I'm the only one who has had a problem with it.  I just wanted to throw it out there just in case.

I have never had this problem but I also almost never use reverb as an insert effect this way. Normally you would create a bus for just the reverb, and a "send" from whatever track you want reverberated to that bus.

I can't reproduce a problem with loss of reverb tails from Breverb after a clip with a short audio transient ends no matter where I put the FX - track or bus - or whether CA-2A is in front of it or not.
 
If the output of the track is silenced by any kind of automation, that will obviously silence the reverb output if its on the track, but not if it's on a bus, as you noted. Reverb tails can be preserved with the FX on the track by using Clip Gain automation instead of Track Volume.
 
I thought your issue might be related to not having Always Stream Audio Through FX enabled, but disabling that didn't make a difference here.
 
If you're seeing something different from what I described, there must be something else going on in the project or SONAR preferences that's causing the problem.

I can't remember which update version it started happening with.  But it was several months ago when I was working on an audio book.  I ended up reverting back to the previous version to finish out the job (the previous version worked as it should).  The book had a "ghost" type character so I added reverb to that voice for effect.
 
I know the "normal" way is to create a reverb bus and use sends....I've been working with analog consoles since the '70s.  But this is just one of my ways of work flow that has worked for me for years with digital audio and using buses.
 
It's just strange that it happens when I have the CA-2A before the Breverb on a bus.  I think it was Bill Jackson that I sent one of my project files to...and he discovered what was causing it (the CA-2A before the Breverb on the bus).  But a solution was never found as far as I know.
 
Like I stated earlier...I can work around it.  I just don't like having something that doesn't "work" as it should.  :) .