If I remember the story correctly ....

The V&T did build the C&C, which started from Mound House, Nevada and built towards the mining boomtowns to the south. The line served Candelaria and the mines in the WHite and Inyo Mountains on the east side of the Owens Valley. As a result of this routing, the railroad did not actually serve many towns or population centers. The "300 miles too long or 300 years too soon" quote is attributed to the owners after making their first inspection tour. The line had been proposed to extended from the Carson River (its origin) to the Colorado River (somewhere around Needles?), and later Mojave was considered but the only additional narrow gauge construction was a short lived branch south of Hawthorne to reach firewood sources and a later relocation around Tinnemaha Reservoir (adjacent to US395 today). V&T sold the line to CP/SP who renamed it as the Nevada & California. Within a couple years, the Tonopah/Goldfield boom hit and the narrow gauge Tonopah Railroad was built to connect to the N&C. SP made their purchase price back in short order. Bt - they were dependent upon the V&T to move traffic from Reno to Mound House for transloading to the N&C. The V&T was still of some value at this time, and after considering purchasing the V&T as too expensive SP built the Hazen cutoff bypassing the V&T, and standard gauged the line to Mina. There was actually a few miles of three rail from Mina to where the now standard gauged Tonopah & Goldfield branched off.

The Jawbone Branch was built from Mojave primarily to serve construction of the first Los Angeles Aqueduct, but SP also used it to connect with the N&C at Owenyo, and later Trona RR connected at Searles. At this time there were some effort to prepare to standard gauge some of the N&C out of Owenyo - replacement ties were standard gauge and some station roof overhangs were cut back to gain clearance. The effort never went past that. I guess there was some talk during WW2 to keep the line since it was far enough inland that the Japanese couldn't attack it from carrier based planes, but instead the rail over Mt. Montgomery was salvaged.

When the narrow gauge was finally abandoned, SP still continued to provide service to the same customers. Instead of the narrow gauge, the trucks of SP's PMT picked it up for transloading at Lone Pine until service was suspended north of Linnie (long gone L-P sawmill outside Ridgecrest). On the Mina end, SP ran into issues with the treaty/agreement that allowed them to cross the Paiute reservation. In the end, SP abandoned between Thorne (Hawthorne station) and Mina. To preserve rail service to the ammunition plant, the US Government bought the middle part of the line acroos the contested reservation lands, but SP/UP operates the trains over it.

What if the line had been standard gauged? I doubt it would have survived. There is just too little local traffic. US395 and US95 killed the passenger, mail and express traffic. There is only a little bit of mineral traffic left - a plant at Appian on the north end and Trona's interchange at Searles. Some of the former Mina customers might be the ones reloading at Fallon which has saved that branch from abandonment (was denied years ago). The US Military has very limited use for rail these days compared to the past, so I don't know how much they are using the line, though they did during Desert Storm.

As a through route - the entire line over Mt. Montgomery has tight curves and heavy grades, so to be useful it would need to have been entirely re-engineered and re-constructed. And it crosses at a higher elevation than Donner Pass but doesn't get the snow since it is in the rain shadow of the Sierras. The Mina and Jawbone branches had some long grades that would not have been inconsequential to operations. And what traffic would it haul? I guess it could have been used in combination with the Modoc to get lumber to Southern California instead of the Shasta and Valley routes, but that traffic isn't near what it used to be. It doesn't really fit as an intermodal route. What unit trains would use it enough to justify maintaining several hundred miles of secondary mainline - especially considering how quiet both Donner and the Feather River are these days. If the Modoc and Tennessee Pass couldn't survive, there is no way it could either.

As much as I would like to have seen four big SP tunnel motors with five more cut in as swing helpers grinding up Mt. Montgomery - it was never destined for reality and I can't think of any justification for it in current times.