According to the PAFX Addendum, you can "use Motion’s camera to pan around and watch your 3D objects interact with the elements of Motion."
"Interactivity" is what I'm trying to acheive...
I've been at it for a while now, but is there a way to rotate PA objects around an object in Motion's 3d space? My guess is no, based on the fact that the PA group has to be a flat 2D group in Motion's 3D space, but maybe someone has a workaround or another idea?
There is no direct interaction between PA layers and Motion layers -- but they can be made to look like they're in the same 3D space.
You're correct in that the PA effect lives in a 2D layer, so a Zaxwerks object can't rotate around a Motion object. A workaround would require two identical layers - one behind the Motion objects and one in front. Then some fancy matting would be required to mask things out properly.