The time is what kills you. Making LAUS a branch line off a main line that extends down I-15 to San Diego is politically impossible as well. But there's nothing in the wording specifying the "via" points that prohibits entrance to LA other than through Soledad Canyon, as long as Palmdale is a stop. They could even do 1/2 of Mouse's Tejon tunnel (to the top of the hill from the SJ Valley) then turn down along the fault from Gorman to Palmdale to make the stop (if money were no object).