I live in Salida, CO, the city that used to be a Division head for the D&RG. From Salida many of narrow gauge lines, including the famous Marshall Pass line over the Continental Divide to Gunnison joined the DR & G mainline.
The UP track from Canon City to Parkdale is where the Royal Gorge Train runs its tourist train. Albeit a very short route there is a variety of equipment and "special" events; dinner trains, holiday trains, etc.
The track rest of the way up to Tennessee Pass, along the Arkansas River through Cotapaxi, Salida, Brown's Canyon, Buena Vista, Granite, and up to Leadville and Tennessee Pass IS ALL STILL THERE! Whatever walking trails there are would be along the side the tracks, or leading from them, not in place of the tracks.
About four years ago a group of local railroad fans (me included) put together a group interested in initiating a tourist railroad through Brown's Canyon, using the existing tracks with the dream of eventually extending further North. We seriously pursued the idea, setting up a non-profit, creating a business plan and enlisting the aid of an existing tourist railroad general manager to guide us through the process and financial needs. We pursued the plan with gov't bodies along the route, from the local mayors, County Commissioners, state reps and senators, the governor's office, etc. All endorsed the idea!
To make a long story short...the UP still owns all the right -of-way and they are not in the least bit interested in selling or even leasing any of their track. It's an asset they value yet will not use nor sell. It took City of Salida years to even get the UP to sell some right-of-way land on the East side of the Arkansas for a small parking lot.
It would seem natural for the Royal Gorge Tourist railroad to simply extend their operation west 45 miles. They have the equipment, the infrastructure, staff, etc. They are not interested because they know the UP. The UP has no interest in giving up their track or rights-of-way. The only way the Gorge route got the track for their operation was because of the courts...when the DR&G was taken over by the UP.
I'll do some Google Map research and see if I can get some recent aerial photos of the tracks along the Tennessee Pass route. Every time I drive through Big Horn Sheep canyon on US 50 where the route snakes along the Arkansas River and climbs up to Salida I can only imagine how it would have been while steam and even diesel would look winding its way up to the mountains.