Those prototype civilian cars...

In Levels 2 and 5, you can see the multistory carparks (by the stadium and construction site) have civilian cars. However, they look slightly different to the ordinary cars found commonly in traffic, as being the early models from development of the game years ago.

~ Compact Car ~

~ Pickup ~

~ SUV ~

~ Sports Car A [Ver. 1] ~

~ Sports Car A [Ver. 2] ~

If I may ask, is it possible for these cars to be made drivable through a mod? I know they don't look much different (other than the first and second Sports Car A in shape appearance), but hey, still a little something as extras. :D Of course, I'm not that much fussed on them, anyway. ^^'

If you have the models you can easily make a mod with these cars as drivable cars. There are a few tutorials as well for custom vehicles

The blue and red Sports Car A prototypes are especially interesting to me as well. :)

And one surprising thing to note, all these beta civilian cars in the parking lots are not actually real vehicles, but are basically props instead. You can get out of bounds and feel their solid models, or hit them to knock 'em away and earn a coin.