My family has a camp near Farmington, ME so I'm familiar with most of the SR&RLRR including the segment Philip mentioned. In fact, a few years ago my so and I ran from Reeds along Orbeton Stream up the grade all the way to the crossing into Redington, where we were careful to stop at the Navy's sign prohibiting access into their survival area. One part I recall is when my son, a ways ahead, came jogging back, thinking he was being a good guy and checking on his Dad, he exclaimed, 'there's a moose on the trail, what do we do?' I suggested we make lots of noise and keep going. The moose ambled off into the woods paying us no attention.
A few years after that, I hiked up the grade but found it badly overgrown after Sluice Hill since the snowmobile trail had been rerouted and no one was taking care of the brush. Anyone been up there recently?