In PA, the following counties have capability to use the frequency as a dispatch to dispatch coordination channel:
Adams
Franklin
York
Lancaster
Cumberland
Dauphin
Chester
Delaware
Montgomery
Bucks
Philadelphia
I hear the freq used frequently in the Harrisburg area for intercounty response coordination. The PA Turnpike Commission also has this freq licensed in the Harrisburg area. The license states it is for interop purposes, although I have never heard them actually using it. Anyone else?
In the Philly area, the frequency is now a back up to the SECOM microwave network that links Philly with Chester, Delaware, Montgomery and Bucks in PA and several counties in NJ (and maybe now New Castle Co, DE, too?). I don't know if the Philly area counties still do radio checks on the freq, but they used to do a roll call on this freq and 155.475. I still hear Chester using it to talk to Lancaster now and then, but the others don't really use it now. Montgomery used to use it daily as part of their VHF fire system which has now been replaced by their trunked system.
I was under the impression that all counties in MD use this frequency for interop. I have heard roll calls in MD encompassing numerous eastern counties, Baltimore City, and USCG.