...My main point is that Fire/EMS *cannot* be encrypted for inter op purposes.
We ran into this in Woodbury. It wasn't encryption.. but for interop. Same principal. Southbury, Bethlehem, Washington, Middlebury departments are all still conventional with Tone, or DCS tone. They have Woodbury's conventional on their radios, and when providing mutual aid will switch and talk/route on Woodbury's frequencies when needed. This is done simply because most of the new radios cannot do/use the OLLLLD interop frequencies in 33mhz and 46mhz range and it would require a entirely different antenna setup and such. Not practical.
Woodbury went P25. Oddly, not a full trunked system, which would have allowed for extra TG's/NAC's. They have 3 repeater sites, linked, with 3 sets of repeaters for different frequencies at each site in VHF band 155mhz range. Each repeater/frequency is for a service. They were intended for Town Services, Fire, Police. The town and NorCom made a big whoopsie in planning, they forgot the like.. 50+ one way receive only pagers for the VFD members (A $40k+ expense...), and Fire Interop capabilities for other towns. Other towns are all analog and would NOT have been able to hear, let alone transmit, to Woodbury frequencies, would would have caused a whole extra issue/need. So instead, to save money and keep things simple, they repurposed and took the Police's repeater, shoved it on the old Fire Conventional frequency/tone, simulcast the P25 frequency to it, and called it a day. Police still have P25 radios, but they operate in Simplex only. The cops in town hate them because they're out of range a lot of times. Luckily, because we have the State Trooper program, they all have CSP Troop L radios in their car already since they're dispatched off Troop L dispatch, and simply use Troop L Car to Car to talk to each other instead. They just use the P25 town radios mostly to listen/broadcast on Town and Fire frequencies for assistance.
So once they start introducing encryption... they will run into interop problems with smaller towns. In theory if both towns are on CSERN, sure they can talk to each other, but there's slim chance of every town being on it. It would be real nice if they started working on some regional Interop frequencies to replace the old 33mhz and 46mhz bands that are still technically in use, but most towns cannot use for the most part due to being on different bands as most towns are on 155mhz, 450mhz, 700mhz or 800mhz systems now.