It don’t think there is an official term for this in french, especially with this opposed meaning pair scheme. So you could fallback on a word game, but with a slighlty different meaning : i.e.: “voiture casse” (a heist car) and “voiture classe” (a classy car, meaning it looks OK and doesn’t raises suspicion, Im’ not so sure on this one, but you get the logic ^^)

I don’t know if terms like this already exists, but here’s an idea. You could say “voiture leurre” (the “red herring car”) for the hot car, and “voiture de secours” (backup car) for the cool car. This way I think it’s clear that the first car is only used to attract attention to it, while the second car is used to actually get away.