Don't know about any of those specific roads, but I can tell you that we have the same problem in Wyoming. Landowners routinely post signs along public roads that are clearly calculated to suggest (without saying so) that the roads are private. The problem is so bad that a bunch of public land user groups got together a few years back to try and lobby the legislature to criminalize the practice. Sadly, nothing came of it.
It would sure be nice if there were some easy way to determine whether a particular road is public. The most informative signs I've seen are the ones that say: "Entering Private Land, Please Stay on the Road." They tell the story well, without pretending the road is private. Old Flowers Road above Fort Collins is a good example of the positive way to handle the problem. For Example "Road passes through private land, next X miles. Please stay on the road"