I've been discussing this whole situation with my Father, and since he has 35+ years in the legal field, he mentioned these three ways to possibly get the line open again:
1: Get a temporary restraining order against the FS.
2: Get a temporary injunction against the FS.
3: Get a permanent injunction against the FS.
With the first option, it seems to both of us that the FS could be forced to back off the C&TS, and the others could cause a more permanent thing. And, of course, the fact that the railroad is not actually on FS land brings another interesting piece to the puzzle.