Dave:
Don't know about EBT. The D&RGW normally used the same weight for all three rails although there are examples of where they did not. In the early days, they sometimes had a smaller narrow gauge rail and it caused problems as the equipment actually tilted.
I shot about 75 pictures in the Alamosa yards in 1971 before most of the third rail was pulled. Managed to see a bit of dual gauge switching with a GP9 using a dual gauge idler to move cars around for the scrapper.
I think the rail was 90 pound on the Alamosa to Antonito line, there was probably 65 and even some 52 pound in the yards. I have D&RGW profile books that show all of that and I will check tonight.
As a note, when the D&RGW removed the third rail from the Salida to Leadville segment, that rail was used to relay Poncha Pass for the 480s.
Other than segments like Alamosa to Antonito, Alamosa to Hooper, and Salida to Leadville, most of the D&RGW dual gauge in later years was in yard tracks and that did not require the heaviest of rail. I am not sure, but I think there was still some 45 pound rail in some of the shop tracks in Alamosa, they sure look light in the pictures. A 480 or 490 could run on 45 pound rail at slow speed. Some of the rail on the Valley Line was still 45 pound to the end.
I have been tempted to write an article on D&RGW dual gauge operations as it is quite interesting and I have some D&RG drawings of dual gauge turnouts. The Grande had a number of engines equipped for dual guage and even some standard gauge cabooses on the Salida to Leadville segment were equipped with dual gauge couplers.
