All of our ambulances have 325P2s, they are used to listen to police (Boston, State, MBTA, the local colleges and surrounding communities,) Boston Fire and surrounding community fire if the user so desires. The bottom line is that it works. It has saved me from driving into an active shooting scene (the dispatcher relayed the message well after I would have been on scene had I not heard the transmission) and I'm sure it has helped other crews. We have XTLs in the trucks and everyone is issued either an XTS2500, APX4000, 7000 or 8000, they have limited interoperability and do scan, but the command staff put the scanners in specifically to avoid the radios being used to scan, as they want the department radio dedicated to the department.
This is not on an overpriced trunked system. Everyone, with the exception of the State Police (who also give their troopers scanners) is on UHF with individual agency maintained radios. People seem to think everyone is using a system where every channel is available to every user across jurisdictions. It is not always the case.