Trunked radio systems, as used by police, firefighters and EMS worldwide are not peer-to-peer. You transmit to the trunk, it relays to people in your selected group. All radios rely on a control signal from the trunk for determining where to send and when to listen.
All our 'digital' signals are ultimately transmitted over some analog channel. "Digital" is an abstraction. There's no reason you can't encrypt a radio transmission without relying on intermediaries to relay it as in a mesh network.
So, a like-to-like alternative is probably a encrypted local mesh network.