'... not supposed
...'. In a perfect world, maybe. The reality is that in a major event, all sorts of equipment, communications and networks are pressed into service. Off-duty responders in area may not have the ability to return to base to get the official equipment, qualified civilians and volunteer groups also participate not only in actual emergencies, but also preparatory drills and exercises.
Probably the best example of this is when the DOD 'defuzzed' the GPS signal during the Gulf War (
.... The number of GPS receivers that they had available that could translate the encoded military signal was not nearly as many as needed. The military bought several thousand commercial receivers, and distributed them army and other ground units. To enhance the role of these systems, the Air Force stopped degrading the GPS signal, so that these commercial receivers could provide 16 meter accuracy.
... from http://www.fas.org/spp/militar...
). Also, military personnel were actually having their families send them civilian units to make up the shortage.
Active Interference with any network is usually a bad idea, the exception might perhaps be correction other secure facilities.