When you import a live Photoshop 3D file into AE you get a pre-comp for each 3D object. If you import two 3D psd files you'll still get a comp with the 3D layer, the controller and the camera. All you have to do is to copy the 3d layer and the controller from one comp and paste them into another comp. That's it. The camera will kind of interract with each layer but the perspectiver changes won't be natural. You can move around the objects to look at them from different sides but that's about it.
I'd put both objects in the same PSD. Don't expect fast renders.
And to answer your last question, yes, it would be good for you to start learning a 3D app. I'd start with Blender. It's free, powerful, has camera tracking, projection mapping, and export to AE.
I'd like to know if it's possible to create a new comp in After Effects (CS5.5) and then import two Photoshop Live 3D models into the comp and then animate a camera around them? I can do this easily with a single imported PS 3D (PSD) model, but can't figure out how to import a second 3D model to use in the same scene.
Nothing to figure out, because basically it can't be done. That is you can of course import multiple files and by rewiring the controller expressions and linking cameras create the illusion, but despite your best efforts the meshes won't interact. As far as AE is concerned, they are just each its separate own little universe. Same limitation as when using otehr 3D-ish effects....
Thanks Rick & Mylenium for your replies.
I guess I'll have to bite the bullet and learn a new app.