Due to SA:MP 0.3 you can now go to a Pay 'n' Spray and repair the following:
Police Vehicles
SWAT Vehicles
FBI Vehicles
Ambulances
Firetrucks
In-fact you can now fix any vehicle which fits in the garage...
Yes, this means that 0.3 is allowing police officers to repair their police cars instead of respawning them!
- have fun guys