They “vehicle” may not be illegal, but representing yourself to be a policeman, medic, and utility serviceman may be highly illiegal. The only problem is that cops may not have justification to stop the cloned vehicles.
The vehicle is illegal. ANY unauthorized use of a registered trademark is illegal, just like copyright violations are illegal. If a police officer has any concerns about a whether a vehicle is actually authorized by the company whose logo it displays, this should be fairly easy to verify with large companies like FedEx and UPS, as well as with local utilities. Those companies know where their vehicles are supposed to be at all times. And sensitive locations, like government or military sites, fuel storage sites, etc. generally have a security guard in place to stop and identify vehicles before allowing them to proceed. It’s probably time to step up verification procedures.