It's really for station alerting. It replaces the old Motorola tones that tripped the pagers and house klaxon or bells. Somehow a study was done that says the old, loud wake up system was hazardous to responders. They said it causes tachycardia and a nervous reaction that is potentially harmful physically and mentally. They think a softer house alarm is better for the nerves. So, you hear several tones, see a printout on the enunciator, and hear the voice alert. If you're on the road, you have to listen to the radio command channel though.
Assuming they're using Locution (which seems to be the hot ticket for semi-automated dispatching right now), it's not only for the "kinder, gentler" wake-up. The primary reason they started using it here in Columbus, OH was to speed up dispatches. Because Locution is IP-based and sends dispatches to the firehouse over network lines, multiple runs can be dispatched to different houses at the same time, while it also goes out over the dispatch talkgroup. If there are multiple runs going out at the same time it might take awhile for a run to make it to the dispatch talkgroup - which inevitably leads to companies marking responding before the run goes out on the radio - but it gets there eventually; you can usually tell when this happens because Locutia (nickname for the female voice around here) will dispatch several runs in quick succession.
It also works fine with pager-based systems over the radio, although the speed aspect of sending multiple runs simultaneously is lost.
Locution also greatly improves intelligibility. Because CFD still uses firefighters as dispatchers and they rotate desks during their 24-hour shift, you would hear several different people dispatching runs in a single 8-hour period; some of them had good pronunciation and intelligibility while others were nearly unintelligible. With Locution it's always that same voice.
We had the same problems here with Locutia mispronouncing street and business names (for example "Meijer" stores were pronounced "Mee-jer"), but they eventually told her how to pronounce it correctly.
One thing Columbus FD does do is put the humans to dispatching runs several times a month just so they don't forget how. Normally the dispatcher just sits there, quickly reviews a run sent to him by a call-taker (also a firefighter) then clicks the "GO" button; from there on it's all Locutia.
I also can attest to the tachycardia issue; I was rudely awakened in the middle of the night many times back in my firefighting days. Anything that will ease that shock is a good thing, although Locutia gets pretty boring to listen to.
