Indestructable Cars??

Last night I was watching my roommate doing takedowns in a freeburn marked man session, and a couple of other players had cars that seemed indestructable.  I have no idea what they were, but my roommate was using an Avenger.  In head on takedown's, was always the loser, and at one point, one of these cars was stuck nose to a barrier.  My roommate T-boned it several times at full speed and with boost on, but couldn't take it down.  She tried 4 times, and never a take down.  The cars looked like Camaro Concept cars, or a little like a Mustang. 

Anyone have an idea what these cars might be?  And how does she and I get one.  I am only about 1/3 the way through the game, but she is more than half, I think. 

Thanks for the responses.