@Cascade
I do believe that it is the Colorado & Southern / CB&Q. It's either that or its the DSP&P RR. My memory is fuzzy with those lines up in the northern part of the state. The one to contact is Will (here on the forums: KLINGER). He works at the loop and also at the museum in Golden. He should be able to help with your questions and with the OP's questions too.
Another place to search around on is the Narrow Gauge Discussion Forum:
http://ngdiscussion.net/phorum/list.php?1
If you ask, I'm sure you get plenty of answers there.
Just my input.
P.s. Cascade: Congrats again on the 10K posts!