I have never seen "emergency" on a police car. As for disabling the police, it is a double edged sword, you can prevent plenty of arrests for "crimes" and prevent any unnecessary brutality, but you also may allow the unpolicing of actual crimes such as property theft, vandalism, and murder, unless of course by then private security companies are something prevalent and cheap enough that anyone could pay for one, and thus said crimes would be harder to commit and have a higher risk.