I think John Craft summed it up pretty well. As a retired railroader I see old friends occasionally who are reasonably senior members of management at both UP and BNSF. The question of Tennessee Pass has come up, since I'm a railfan and would love to chase trains there again. Never say never, because the world changes, but all the folks I've talked to at UP and BNSF suggest that the chances of ever seeing another train actually over the pass are between slim and none. I believe UP has on occasion used the line to store surplus equipment, so perhaps an occasional train on the east end is possible. And certainly perhaps a work train for some odd reason. My guess is UP has not pursued actual abandonment for some of the reasons voiced here: they're in no hurry, it will be a messy political issue in Colorado, and perhaps they just like being able to keep control. I would be very happy to be dead wrong in all this.