What is probably going on here is that the Authority is trapped by the extremely fast 2:36 timing between SF and LA that they have promised. As the citizens of valley towns start asking for more features, e.g. 75-foot-high viaducts, HSRA is beginning to realize that the only way to make the time is to shoot straight on over. This means throwing Lancaster and Palmdale to the wolves.
The irony is that if they slowed the train down -- I know, this would mean going back and changing the law -- but if they slowed it down it could get over the Grapevine with fewer of the issues of grade and seismic problems that people have noted.