Just FYI the Hot lines/FAPERN/UASI Calling etc. etc. are used like that so more than 1 dispatch center can hear the message at the same time, this speeds things up and allows for better operational awareness for departments close to the the incident but not involved yet.
Let say I was a dispatcher, and I worked at a regional center, and I had 70 channels on my console and I actively use about 14 all the time, and the rest were used sparingly but in times of need, I would want to be able to use 1 channel to talk to mutable centers to get my message out quickly, instead of making 4 or 5 phone calls while managing the incident, and taking 911 and routine phone calls