The Colorado Railroad Museum had an annual a number of years ago with an account of surveying for the D&RG/RGW in eastern Utah for the ng transcontinental. The surveyor, who was the subject of that story, was noted as later working on a survey for the Rio Grande west out of Salt Lake City into Nevada.
Many, many surveys were made for lines never to be built. Some were for a real extension that was never built -- others were surveyed to scare off the competition. I read a quote of a UP official in the 1880s that it was cheap to survey routes as opposed to actually constructing them.
It is said that the reason the Union Pacific acquired the Nevada Central was to keep the Rio Grande from obtaining that ng line in central Nevada.
Brian Norden