Need to look up details at US DOT web sites. If the project is still more or less using the preliminary plans that were in the EIS, the permit really is for the r/w, not just the median. Some places, it'll be in the median, some places off to the side. Depends on grade & other considerations. I suspect there is a change from the early engineering at the pass itself, where there was originally going to be a long tunnel. Again, need to look up details at US DOT; there should be an Environmental Revalidation floating around for NEPA given the age of the original document and the probable adjustments.

Electric HSR trains can handle grades considerably worse than those used for conventional railroads, but 4%-ville is still a typical target for the maximum sustained grade if a good speed is wanted. That means some tunneling, or a bypass, is needed at Mountain Pass.

Wasn't there a scheme at one time to use nuclear bombs to dig a deep cut through Mountain Pass? Or was that something else out toward Needles?

Other trivia: the Mountain Pass area is still, if I understand correctly, the only rare earths mine in the US. Unfortunately, the product of it is considered a Chinese import because it all is shipped to China for refining. Your Prius might contain rare earths (mostly in the motor magnets) from Mountain Pass.