Impersonating a cop is a big no no. One man in Florida found this out the hard way after he flashed the fake police lights in his unmarked Dodge Charger at an intersection in order to run a light.
When it comes to following traffic laws and I see cop cars, firetrucks, ambulances, city transit, delivery trucks even. I would expert these individuals to be driving around as trained operator's and "expert's" and thus held to a higher standard.