Maybe........... there is redundancy in the multiple channels (repeaters) that are available at a site but the controller that assigns channels and checks radios may not have a redundant backup. When the controller goes down the system can go into "failsoft" in which each repeater operates independently as an in box repeater or several other configurations. The controller at each site may or may not have a redundant backup in which each site can go into site trunking and not be connected to any other site. So there are many layers and configurations of redundancy that can be designed into a system mostly dependent on "how much money you have to spend" on redundancy.
BB