This myth is based around unusual police cars spawning around Vice City. They have a different livery compared to usual police cars, as they are white in color instead of green. They can be found spawned where other civilian cars spawn, whether it is in a car park or on the side of a road, they never spawn in police stations. They also have the exact same handling, engine power and horn as the standard police car. Due to their livery, they are similar to the beta police cars.
This can be easily debunked as a simple glitch. This happens because cars normally spawn in different colors, and since police cars are just normal cars with extra code, the game thinks they are supposed to have the different texture, yet this is rare because the files are not supposed to be used.
This is interesting, as the white police cars are buried deep in the code, which is most likely the cause for the rarity of the glitch.