Just by random chance happened to stumble across this siren coverage map for a large chunk of Iowa on the website for the local ABC affilliate (KCRG). It doesn't provide any information regarding siren models or ages and the actual coverage it indicates is questionable due to iffy estimate figures (More on that below), but it does provide a good overview of siren locations.
http://www.kcrg.com/sirenmap
Most notable is the DAEC siren system right dead center of the map. Unfortunately, life happened and I never did manage to finish the DAEC map I was working on (And some of what I did finish is now obsolete due to upgrades). It's good to see a completed map like this online.
Admittedly, most of the sirens they seem to have just assigned a range of one mile regardless of actual model or range. Needless to say, a 2902 does not equal a 2807, which is what the map indicates for my hometown. But, I imagine lacking further information, one mile is a good "safe bet" estimate to go with, but would be curious for other opinions. With that said, I'm interested to know what the siren is in Jackson Junction (Top center of map) that's been labeled with a four-mile radius.