Yes, came upon it by accident one day with my riding buddy exploring a different ridge passed Rowher flats (he is on the xr 400 in the vids, and he is getting a dr 650 shortly) coming over the back side (many climbs and down hill from old fire roads that appeared to not been used for many decades and turned in to single trails, some pretty rocky and steep).
We had a sandwich, and then decided to leave in a different direction. That's when we did come upon a large chain link fence with a gate which covered both sides of the hills next to it (had to ride upon the side of the hill and do a quick U turn side ways or else "splat"
The following week end we showed Todd the area (the vid he posted), and the very next day (Monday)my friend took a different rider (his day off) to show him the area. The grounds keeper showed up and told them not to ride there because of the bike tracks don't fit with the movie filming of horses (originally we thought that it wasn't being used) .
Well? I guess we won't be going there any more
time to explore new places, but we don't have as many places as You do up there in Oregon.