My father was a civil engineer, and I remember asking him at one point why it was never done before. His answer was simple, once you hit the Grapevine, the mountain range was so unstable and irregular, they could never build a tunnel or pass over it that could be stable for high speed rail and within cost range. It was "undoable" from an engineering perspective. So, the best they could do was run high speed rail from the North down to right before, than drive people to LA or vice versa at that stop point (kind of what they do with Amtrak at Emeryville in Oakland versus going all the way to San Francisco). Of course, no one ever mentioned the Grapevine issue when this boondoggle got started again.