Police sirens are, in fact, bugged. They are not as loud as they should be. This is due to some BI update or bugged script.
The police lights do work, though. The sirens are just way too quiet, and this is the only issue.
I think @Gnashes is aware of this.
It's quite annoying when trying to turn on sirens as an officer and then being told that they didn't hear the sirens.
Let's hope a fix comes soon.