Yes, the BMW's the cops use are K series, and they are water cooled.
On CHIPS, I have seen several different bikes. There were moto guzzi's, but when they would wreck them they used to use Honda CX 500's or CX 650's. they look like the moto guzzi where they engine is a V that sticks out on either side, but they are water cooled, and at the time were cheeper then Guzzi's to crash. I have also seen "inline" motors on some of the bikes which would not be the CX or Guzzi's.
I know Atlanta GA used BMW K100's in the 80's, I still see some for sale on Ebay every once and a while. In Phila they use HD's, no idea why you would want to ride an air cooled bike in the city all day.