There is a system in force over here whereby cops can run a plate in seconds to determine whether or not it belongs to the car that it is mounted on. The cop doesn't even have to do anything other than pull the tw@t over if the plate is phony as it's all done by a computerised camera system that is hooked directly to the MOT and if the plate is good, nothing happens but if it's phony, off go the bells and whistles.
This also works on out of date plates, ie plates that do not have a current or otherwise invalid tax sticker on them eg, your birthday is March, the car/plate is registered to you but has a December sticker on it. (Vehicles in Ontario have to have their tax stickers renewed on the birthday of the owner.) Therefore the plate is run, the info comes back that it belongs to Fred Smith born March 15th 1987 and here it is with a December plate on it. Woop Woop Something is wrong, the plate has been phonied up with a stolen or modified tax sticker. Alternatively the plate might not belong to that car, in which case it doesn't matter if it's out of date or not, the red and blue lights will be flashing in your rearview
I guess the camera/computer combination can run hundreds of plates a minute so if a cop is driving down the highway and a bogey pops up he either pulls it over or if it's on the opposite side of a divided highway, he simply radios to another cruiser on that side to watch for the car/plate in question. I don't rmember what the system is called but apparently it's bloody expensive so it is only being used in certain locations for a period of time then moved to another location.
It's a similar system to that used in certain cities in the US for parking control, they just have to drive by a vehicle and if there are any outstanding warrants or tickets against a plate, the word goes out to a tow truck driver who tows it to an impound centre or failing that, the parking control officer simply puts a boot on the car until it can be dealt with later.