Santa Fe actualy did a Bakersfield - LA track survey back in the 20s, and they found a suitable alignment over the Grapevine with, as I recall, surprisingly few tunnels and a grade that was more moderate than you might expect. The killer then, as it would be now, was cost. (Got this information from Gregory Thompson, who wrote a book called "The Passenger Train in the Motor Age." Interesting study which showed that as long ago as the 20s the railroads were losing money on passenger trains, but didn't realize it because they lacked sophisticated models for calculating the true costs of running the trains.)