Based on her uniform and apparent equipment, plus her manner and apparent skills, I'd guess they're some combination of security guards, mediators, judges, and quite possibly counselors. Antigone Stone seems well equipped for most of these functions...
Add "rights enforcers" to the list. She did seem to mention Seamus having a bond on deposit with her company, therefore providing a surety of his agreement to binding arbitration in the matter of the two anonymous assassins he and Nicole zinged DRT in the corridor, didn't she?
A guard gets paid to prevent such things from happening. Antigone Stone is obviously somebody who only gets called after the fact (note the enraged squawks of the hotel management clown), so strike "security guards" off