I'm talking in the context of a P25 trunked system. Should have been clear about that in my previous post.
Unfortunately it doesn’t always work effectively on P25. In cases where a county is covered by multiple sites, you can’t guarantee that the alerting talkgroup will light up all the necessary sites, unless you set it to always light up all of those sites. That’s fine until one or more of the sites is busy when you try to page a run; if that happens the transmission is bonked unless you’ve got it set up for either hot start or all start (I forget which one, think it’s hot start), in which case it‘ll hit the sites it can hit and ignore the others. Then some people might miss the run.
On top of that, there‘s an NFPA recommendation that the alerting system and the voice system be separate. That way if one craps out, you’ve still got the other to use for getting the word out.
We had these issues at my last admin job before I retired (and other counties in Ohio still have the problem); there were just too many variables to worry about, so we elected to repurpose one of our 800 MHz conventional repeaters into a dedicated analog two-tone paging repeater. Worked like a charm (still does) and cost next to nothing; we were even able to program it into the backup zone as a voice repeater so that if the P25 voice system crapped out, we’d have a conventional backup to use, along with the 700 and 800 MHz interop direct frequencies for fireground.
Two-tone paging is still simple, highly effective and relatively inexpensive. High tech/new tech isn’t always the best answer.