Ben
Are they PA ArNG or regular Army? Here in MD the ArNG guys use a different callsign when they are working with local law enforcement.
I always assumed that any helos I was hearing on the state's TRS would be PAARNG helos based at the Gap or Johnstown...didn't think they would spend the time and money equipping anything else since transients could just use the Army lowband.
The OH-58's that do counterdrug ops here use "Boise" callsigns on civilian ATC...not typically very formal with callsigns on the actual local LE channels (usually just "air to ground" since it is a civilian LEO talking to his counterparts).
Mystic and Bandit are the two callsigns I usually hear from Gap helos...with the occasional helo just calling as Guard-### on ATC. The Mystic and Bandit callsigns seem to either be related to pilot or mission...not sure, but I know by the radio RID that it isn't the same bird using a particular callsign all the time.