Yup. In an emergency most first responders can just wait for the system to come back on-line. HAMs can build a radio out of scrap and start transmitting.Mneawhile, all the 'users' on those mighty-fine trunking systems hear a low-level beep as the controller attempts to re-boot and come back up (thereby restoring order to the system).
Oh - did I mention?
While that 'controller' is booting literally THOUSANDS of "first responder" (and bus driver and trash collector etc.) radios on the 5, 10, 15 or 20+ trunking system 'scan' for the control channel and NOT FINDING ONE will park on a pre-programmed voice channel where it becomes one huge "CH 19" party line where everybody can here everboy else (think busy intersection but now with a "blinking four-way stop" system instead of the usual staged Green-Yellow-Red light system).