I'm kind of wincing at this one.
One or two movies and their attendant publicity aren't reason enough to keep a railroad operating.
Ostensably, the reason for the ICC refusal to abandon the Silverton Branch is because Tourist traffic was growing and that the railroad was encouraged to develop this new source of revenue.
As far as the Cumbres Pass line goes, it seems to me that the revenue generated by the development of the "Gramps" Oil Fields and the pipeline that was being built was more important to the D&RGW than any movie publicity overflow.
When the D&RGW wanted to abandon the Cumbres Pass Line, their will was evident. There are many accounts of customers ordering Box Cars or Stock cars and at the given time a Rio Grande Motorway truck would show up. It was the trip by the National Park Service that really brought the salvation of the Cumbres Pass line to attention at a National Level.
The movies may have helped, but to give them sole credit is to ignore the work of others behind the scenes, like Alexis McKinney. He was a newspaper man, worked to save the Silverton and was later hired by the D&RGW to develop what was then known as the Silverton Train and "Rio Grande Land". He went on to be the D&RGW's chief of Public Relations. He was a wonderfully nice man who believed in what he was doing and after his retirement from the D&RGW supported the Colorado Railroad Museum and their efforts at preservation.
Rick