I've heard of local PD paying for tips/information on things like petty crimes and misdemeanors (though, maybe not parking). I have no proof of such a thing, but I can't see why they would not do it if circumstances allow.
> If I witness a hit-and-run
IANAL, but I suspect that's the important distinction. You witnessed something, you didn't search for it. Just like these Best Buy technicians witnessed the illegal/contraband items.