I was getting my fleet vehicle serviced at a local Ford dealer a few months ago, and the service rep asked me if it was a police car. I had tinted the windows very dark, and he said a local police department had 4 cars that looked exactly like mine. The dark windows conceal an array of cameras that they use for the same purpose. They had most of them in for service frequently, as they put in more electrical equipment than the car could handle. They were having major issues keeping the 4 batteries charged. I have seen them cruising thru the local malls and parking lots, and they seem to be working out very well. I talked to an officer 2 weeks ago at the same service location, and they said that they make frequent arrests for warrants on drivers that own them. They even added 3 offficers just to handle the excess work from those arrests.
Be careful, and keep your tickets paid, or you might get arrested in front of the local Wal Mart...