Not all have implemented it yet. But if you haven't. You were supposed to implement some kind of robo calling mitigation plan (Or atleast certify that you have one). At $dayjob we're fully deployed (inbound and outbound).
I received my first ever STIR/SHAKEN signed (iPhone Check mark, highly scientific) spam call on my personal Cell phone on 6/30. It was a Telnyx number. Had the call terminated to $dayjob network. I fully would have collected all various information and ticketed it with Telnyx.
Time will tell how truly effective this is. But we have better originating information now (breadcrumbs) to follow back to the source.