I scouted this today. Posted or not, it's a utility company right of way on private property. Enter at your peril.
That said, I didn't see any access to it. The north end at Park Hill is 20' above the road, the south end off of Marker would require a long ride across a farmer's field. I must have blown right past the road you marked just past the dairy, but it sure didn't jump out at me. Looked like nothing but driveways.
2014 KLR650 NE