There are a lot of fire horns still in use, though they aren't as common as sirens. Many were installed during and after WWII so sirens could be reserved for civil defense. They seem to be most common in California and New York/New England. I'm referring specifically to diaphragm "tyfon" horns or self-contained "Shrek horns," not diaphones. Here is one person's video:
https://www.youtube.com/watch?v=fBMj2amDb7c