Thanks for all the info! My in-laws also have a paper road over their farm, extending from the end of the road they live on. They live pretty remote but occasionally have someone show up with a campervan wanting to traverse it. A quad bike might make it, but not a car and definitely not a campervan. The paper road is pretty extensive too, tens of kilometers long until it meets up with another (actual) road. I'm not sure what there is at the fence line between farms.
They farm the road, but pretty sure they don't have a sign saying "public access" on the gate. I doubt they have heard of that requirement!