When you do any construction on pretty much any rural road, you have to move all the mail boxes back at the beginning of the project to get them out of the way. We where always required to play them back at 4 ft from the new edge of pavement when finished. We would not put any of them back if mounted on 8" iron pipe, rail road rail, rail cross ties, or anything else obviously dangerous. We would have to provide a plain 4x4 post type and inform the owner. What they did after the fact we never followed up on.
Any work performed in the county RoW was suppose to have a Right of Way use permit; but even when I got put on permit duty (instead of road construction inspection) I would never go looking for un-permitted work, unless it was reported by a neighbor. We where, as a county, often used as a weapon in neighbor vs neighbor arguements.