Seems a bit of a waste to have to stick a channel tool on a bus track just to flip the phase.

Or is it there somewhere and I just don't see it?

Track (Bus :-)) Inspector?

Not seeing it, or I can't see the forest for trees.

  Every audio track has a phase invert switch, but I don't see any on a bus track, looked at inspector and the bus i created in the console... nada. 

Insert stereo bus, no phase switch.

Sorry - I was thinking of Interleave.

a phase invert switch doesn't make sense for a stereo bus.

what are you wanting to do with a phase inversion on the bus?

+1.   The Phase button is actually (AFAIK) Polarity, which can only exist where a wave file is.
 

For example you stick a PC4K gate on a bus, use something like a kick to trigger the sidechain then stick the EQ after the gate.

Now you route something like a large bassy pad though the bus but also send the signal via a send to the master out and flip the phase on the bus.

  Everytime the gate opens you get phase cancellation of whatever frequencies you carve with the EQ, this way you have something akin to a sidechain EQ instead of duckinf volume you duck the bass which is a lot less noticeable in the mix.

Just one example, lots of fun can be done playing with phase cancellation.

That is interesting.  I have often seen people clone tracks, reverse polarity of one, and then use EQ sweeping or other effect on one track to create an interesting sound (like an extreme wah-wah or a quasi-envelope-follower sound), but, to Beagle's point, this requires recorded audio.

Although that is definitely a creative use of phase cancellation, how about just using Dynamic EQ (e.g. Voxengo GlissEQ, BrainWorx DynEQ) or one band of a multiband compressor on the bus to reduce only the bass content above a threshold?

I mostly did it this way because I needed the ducking of the EQ to be based on another track and I couldn't find any way to automate it, drawing in automation would be a nightmare.

It's a nice way to have 2 tracks that competes in the same spectrum without compromising one or the other by applying a static EQ or volume ducking with a sidechain compressor. When one needs the room it ducks the spectrum it needs on the other track. Done with bass in a full mix you can hardly hear it's being done.

I'll have a look at the EQs you mentioned.