Since this is a city government system, why not just license the EMA/EOC with Part 90 equipment? Using GMRS/FRS for the purposes stated may not be reliable under some circumstances (interference from civilians) and may be abused unless everyone using the equipment is individually licensed and trained properly. I'm sure that someone in City Government already has an FRN for licensing other agencies, so a Part 90 license for a few 5 watt handi-talkies might be best all around. There are several Itinerant frequencies available that do not need frequency coordination and will probably have less outsider traffic than using FRS/GMRS.