It seems it only becomes a legal issue if the person being photographed has A REASONABLE EXPECTATION OF PRIVACY.
Well, I suppose that a person doing their job does not "reasonably expect" someone to take their picture while they are unaware and post it on the internet. Very poor form, in my opinion.
Well, those workers are on private property, not walking the public sidewalks or out in a public park. In fact, you are on private property, so permission for you to take pictures might be required. There is no "The Law," unless you are talking about California statutes. I can find vague references to individual state's privacy and photographing laws (as well as Federal ones discussing nude pics), but nothing that's real specific. I would have expected this to be as well-documented as statutes about recording conversations (which vary widely by state), but it does not seem to be. At least, not by my cursory search. Which is weird. Photography is way more common than voice recording. Personally, I don't have a dog in this fight. I don't really care. And the guy is wearing a mask. But if anyone in that transaction has exposure, it is you.