Surely they don't get paid if they are not authorized to perform that service?
That's not the case here. The Sheriff said permission to do what you're describing is not given in their jurisdiction (nor most jurisdictions). My family lives in a place where people get per diem money for being a (once in a while) deputy (no blue lights, but they do get $ per call - they just use their own cars and everyone knows that using one's emergency blinkers whil driving fasts means you're dealing with a part time deputy).
Sheriff got on the stand and said that's not done in the jurisdiction in question. And where I live, all EMT's have to have insurance of some kind to do their job - just like any other responsible person who might incur liability. Yes, it's a status symbol to have lights on your Suburban or whatever it is. Most people with those lights are decided not EMT's in most jurisdictions - it's quite scary to have unregistered, non-public employees, non-LE driving around with the ability to pull people over. Serial rapists do that, and serial killers.
Even "qualified" people (like Alec Murdaugh or certain doctors or certain policemen) are capable of murder. So it's not okay to impersonate a police officer in most places (Alec even had two expired badges!)
I'm glad they need permission for the lights where you live - where I live, no one gets that permission except people who are part of a registered police force. Sadly, that also includes so-called private police, which is scary.
IMO.