A tenth of a trillion dollars to build this?!? A round trip flight from LA to SF costs about $100, which means you could provide just under one billion round trip flights between LA and SF for the same price (and reduce travel time to 1.5 hours).
Let's say for the sake of argument (and because I don't know the real figure) there are 10,000 people who travel between LA and SF each day. For that same tenth of a trillion, you could fly each of these people return, every day of the year, for almost 274 years.
Like all things managed by government, the economics come from bizarro land. It's like reading articles that a government is "investing" $300,000,000 in order to fulfil "short term housing needs" by providing 1,500 "permanent beds" for homeless people - make you wonder why they don't just give these 1,500 people $200,000 each (except that $290,000,000 ends up spent on the bureaucracy to "support" the exercise).