Not sure what you mean, but you can have a parent track that has parent motion in 3D. With the parent motion you can move around looking at the composite child tracks.
I think that might be able to do it. I might need an example. What i am trying to acccomplish is 2 layers. one in front of the other, and have a "camera" in front of both of those looking at the 2 layers. The camera moves from left to right, and the depth of perception is maintened by the 2 static layers which are seperated by distance between each other.
Have a look in the new features pdf, downloadable from here (lower right): http://mediasoftware.sonypictures.com/products/vegasfamily.asp
There's a section on "Enhanced track motion tools" and one on "3D motion and compositing". You might have all the answers there.
Best/Tommy