Keith:
Leadville was probably the most interesting mixture of standard and narrow gauge around. During an 1899 major snow blockade, there was four rotary snow plows in Leadville on the same day...C&S narrow gauge plow, D&RG standard and narrow gauge rotary, and the CM Jull plow.
Dori Osterald's "High Line to Leadville" book has an excellent map of the area with all the mines and trackage shown.
Several of the lines used trestles to cross over the competitor's lines, but the D&RG's Ibex branch and the C&S high line had a crossing. At one time, both lines were dual gauge, so it made for an interesting mass of rail. There was no control other than visual...they just looked out for other trains. Sometimes they didn't and there were wrecks. At Gunnison, a C&S narrow gauge train once collided with the D&RG's Crested Butte branch. One of the few times narrow gauge trains from two different lines met that way.
Jerry Day