And in [almost as many as you Gary] all my years of monitoring, I have rarely heard or heard the need for a
LEO to cross-talk to a FireFighter on their respective channels. Outiside of Dispatch/Command doing this.
But then there are those [ROTFLMAO] who think the maintenance guy needs to talk to the PD who need access to the Housekeeping channels.
One notable Exception was this past Christmas morning, and the FD was dispatched to the "Wrong Street Name"
way across the other side of town, On-Scene LEO [who also does much of the Radio Licensing etc]
had to straighten out the situation by coming up on the FD channel and giving the corrected address location
Also he having been an FD and EMT, provided the hydrant locations and exposure info for situational awareness
for the in-coming apparatus
There are multi mode radios, but I also wonder how often units from one agency need to talk to another.
Boston PD, FD, and EMS radios have an interior channel and I never knew of any instance where it was used.