When towing and the other person is not, they can either back up, or I will move over as far as I feel comfortable with road and overhead, then they can choose to back up or try to pass on the berm or whatever. Up to them.
Now I did have a situation 2 summers ago where a young girl drove up and took my turning space when I was in mid-swing on a narrow 90deg turn and then tried to wave me to come on.
There was some hand waving on her part, some inching over, then eventually pulling to the edge, but pretty sure she realized her mistake when I did (barely) make the swing, nearly taking her mirror with me. I was on a solid 9% plus grade, utility trailer fully loaded, and already into the corner.
Sometimes it takes a bit of time for non-towers to realize the situation, but I have all day vs damaging my rig ;)
Now I am also the guy who quickly and often first finds a pull off when someone is coming the opposite direction and I can manage it- whether I'm towing or not.
Tip: If you are SURE there isn't room to pass, stay in the middle of the narrow road with your lights on. Otherwise, you *know* someone will try to squeeze and get you both into a problem :E