My two cents
For agency initial notification:
-our county consolidated 911PSAP (Pike County, Illinois) creates a CAD incident, which automatically flows into a text message addressed to the agency responders,
-AND the same text message automatically flows to an application provider which 'pushes' complete incident information to a smart phone app,
-AND the dispatcher sends analog radio paging signals and voice information to the agency's local analog transmitter, which sets off traditional pagers,
-AND a central high-power radio automatically repeats all paging signals and voice from a second location after a fifteen second delay, which sets off most pagers again, and can be heard by any radio county-wide (which gives excellent situation awareness to possible mutual aid providers),
-AND if the agency doesn't respond after one minute the whole process is repeated,
-AND if the initial agency doesn't respond after two minutes automatic mutual aid is notified the same way,
-AND the paging channel is only used for initial paging; we have two interchangeable repeated command/control channels for response and coordination,
-AND every radio system is independent from telephone and utility failure, and has a redundant backup.
All departments issue traditional pagers (or radios with paging capability). I carry a pager and my smart phone, plus (an occupational hazard) I have live radio audio running 24/7. My pager and smart phone app both require that I shut them up, lest they keep going off for hours. If I miss a page, it is probably intentional.
With all of that in place, we are fairly confident that agencies are going to get the word that they need to put their boots on, and can coordinate response on a county-wide basis.
ISO likes it just fine. My rural volunteer department is a "4", and could be a "3" with paid staff and bigger water mains.
None of the ten fire agencies in my rural county run station sirens for fire alerts. Reasons:
-Last time we checked, this is 2015. There are better methods available, and all of them carry more information than 'Y'all come quick!". Station sirens have gone the way of pagers going off with every wrong number and telemarketer call to the station, and fire bar phones ringing at the diners and gas stations.
-All sirens can still be set off locally or by the 911PSAP; the extra rope for our belt-and-suspenders backup plan.
-Only half (if that) of responders live/work where the siren can be heard, and even fewer can hear it inside a modern home with the dishwasher or TV running. I live more than two miles from my station, so that isn't happening.
-Sirens do a fine job of alerting Robby Rubberneck (less of an argument now that Robby has a scanner).
-Sirens carry little useful information for responders. There is no difference between a siren alerting for a major fire mutual aid call and a siren alerting for a minor response to an incident one block from your home. The latter certainty doesn't warrant a blue-light-special speed run to the station.
-Not all sirens operate without public utility power.
-Sirens are more suited for mass public warnings, and use as a fire notification is confusing to the public.
All but two departments have upgraded the station siren to weather warning devices. The 911PSAP can active them remotely one by one, or by region. Full test every Tuesday at 11AM. All year. A couple "bump" every day at noon. We don't want to wait a month to find out we have a failure.
As far as sirens confusing the public: do you know the different meanings of a 1-minute wail, a 5-minute wail and a 3-minute solid? Do you think your grandmother does? Wouldn't it be easier if ANY siren meant that you should head to the basement, or at least stick your head out of your hole to see if the sky is falling?
And as far as apparatus sirens go, use common sense. Going to wash the roadway at an accident scene doesn't warrant sirens, and probably not even en-route lights. But if I'm driving to a time-sensitive incident and pose a hazard to the public or myself, it's going to get real loud even after (almost) stopping at every red light and sign. I'm not going to create another incident. Sorry about the noise. Go back to sleep. Get over it.