@AaronMk  
I was also told that it was probably a removable vinyl wrap thing.

@Smudge_Proof  

 
I’m willing to bet they could be painted, in which case they go into storage or are auctioned off. Or they were already bought and custom made by someone for the event and could slip away to some private garage.
 
I’m willing to go the route of them being an advertising prop for both parties. If they wanted to do it on the cheap then the car’s a shell with the lowest-grade engine there possible just to get them from point A to point B, or from trailer to display place. I’ve met a few people who do display work for cars like this and that sounds like what they do; build just the chasis and the exterior components and skimp out on everything because all it needs to do is look pretty.
 
In that case it was new cars for the Detroit police department and they were doing a showing for the press and all they had at the time was basically a fake car.

So are these sort of cars, is this painted on, or some form of sticker print job? Whatever happens to these vehicles after the marketing campaign is over?

a mustang would be a better choice of car !  
(or Hyundai Pony, lol )

Oh for fucks sake, a Korea US designed Daewoo Chevrolet Aveo Sonic? Could they pick anything worse?  
Chrysler Sebring 200 comes to mind  
HOOORAY FOR THE CHEVROLET!

ANGRY HEADLIGHTS.