Run to catch. They do phase in vehicles, they do not all get replaced at one time because they are not all the same age. All vehicles for the state, and municipalities are ordered through the state Dept of general services who puts out a request for bids on the vehicles. The vehicles are sold at fleet pricing. Whe ever needs the vehicles sends what they need, police package autos and SUVs, pick up trucks passenger vehicles vans etc. I just saw a new Chevy that our twp police dept just put on the road, it is also black. After the PGC receives the vehicles they are outfitted locally by vendors, install emergency lights, radio ect. Much of this equipment comes from vehicles that were removed from service and given to General Services for the next vehicle auction. Most of the time the vehicles are all the same brand. Going through GS and bulk buying saves ever agency a lot of money.