I seem to recall that there's a Defcon talk to this extent—one of the many that talk about locks and keys—that shares that (some) police cruisers across the US use the exact same keys, proven by showing the showing a monroney label on a still new police car which listed a barrel type had an already publicly-known key pattern.

This is the case - New York cop cars and New York cabs had the same key because the latter were often old copies of the former.

And all elevators in the USA have the same key, and you can buy a key set with almost all tractor keys.