You can. Just take a shot with the only car you have. Then, go to your library and select the shot you just took. Press triangle or options and "go to location". You'll now have your car there but you can add it again. I found this out because I wanted to have 3 different liveries for the same car in the same shot.
If you select "go to location", your car is already in it?
And also the same angle of the camera, camera settigns, car settings etc? Because I can imagine that adds quite a bit of data to the scpes-library
Would be nice though....have to try