As for OP it's a police car, and they almost always have camera systems.
As for regular drivers:
In Russia it lowers your insurance (some even insurance companies now demand it even.)
You can buy a cheap good chinese car camera for around 70 bucks.
The plug in the cigarette lighter, and when you power on the car the camera starts recording, when you power off it stops. You just put in a big SD card and it starts making loops of 5,10,15 minutes, when the card is full it erases the oldest loop.
I have one but so far nothing exiting has happened.
Also do mind that in Russia/China car crashes happen a lot more frequently.