They were on a lot of buildings. Yes, a lot of fire stations had them, but so did a lot of public schools and even private businesses had them. Enterprise oil was a company that had a tbolt, it had been removed though. There is also a tbolt on a company around
Pulaski and Wrightwood. It was there as of 3 years ago.
mod edit: added hyperlink to Google Maps view of siren in OP.