We used FM, allowed or not, when any of the locals got the urge. I'll also say that most of the locals, well basically all of them, had FM on one radio or another, and it never sounded very good for local chit chat despite being FM, also did not work well since guys were spread all over and signals varied greatly. Had it been an amazing sounding mode for everyone, we all would have used it, most had it already, but it just wasn't pleasant with the radios used. Nobody liked using the squelch either, and sometimes guys would hop on the channel with a signal you couldn't see on a meter, but could hear them on AM / SSB, so with the squelch set / FM, you'd never have heard these guys.
Still, I don't know why FM on CB wasn't legal a long time ago. Seems like a mode that would have been good for CB in many instances.
Suppose it will be interesting to see the various radios it gets added to.