When I was doing my Paramedic training with SBFD, they had what they called a "tap", where the PA was opened in the station, presumably by phone line, and you would hear the pop sound of the speaker opening and there was a single tone announcing a medical aid or other basic response. As for a structure fire, I can't recall what the particular sound was, but I never heard any QCII or any other "paging" systems in use by them. This was 8 years ago or so and it may have changed, but that's what I remember......
Mark