Philly is like that. They have police "boxes" on street corners with blue flashing lights on top of them even. If the camera detects a crime, it flashes and sounds an alarm. Criminals ignore them.
This isn't for a government controlled system however. Individuals would use them as a type of neighborhood watch instead. When you, as a criminal, drive into my neighborhood, you had better have a mask on and disguise your car the entire time.
If you did that, people would immediately call the cops though. As long as you are peaceful then, you are fine but being recorded. If a crime is committed, the people in the community have your vehicle information and the pictures of all the criminals. It would help a lot.