No, they actually crash cars. At least I assume they do, because that’s what they do in the movies, which is actually cheaper than paying an FX house to create a realistic 3D car crash.
To an auto company, ruining a handful of $20k-30k cars (that’s retail price, mind you) is a drop in the bucket when the overall cost of the commercial is usually well into the millions.
As for insurance, I’m sure that sort of thing is worked out, or dummies are used in the crash. Again, they’ve been doing this sort of thing in the movies for years. Google “Remy Julienne” for the first class example of stunt driving.