Local knowledge here, absolutely no encryption used on any NXDN channel. Tac channels aren't used either, everything is on the main dispatch channel or thru a phone call. Most SO calls are done thru MDTs, 7400 will say "signal 9" and that's it, occasionally the call will be said though. Oh! And everything is 12.5 kHz/9600/Narrow NXDN, instead of very narrow.
Some volunteer fire departments have access to NXDN radios, at this point I think most depts. have newer radios. All EMS stations and Bascom EMS have NXDN radios and you'll occasionally hear Bascom standing in for TFD's medic. Not too sure if the switch will happen soon but county fire dispatch may go NXDN as well.
Also, I occasionally hear deputies in analog since the radios still have the analog channel programmed. Dispatch can't hear analog from what I've picked up on but make sure your scanner is running mixed mode so you can hear if that happens.