Well, keeping in mind that this is San Francisco we're talking about here, 11 figures of funds needed isnt exactly out of the question, its definetly not something we've never seen or heard of here before.
To get something like this off the ground, you're gonna need the approval of the public (something that might be a little difficult to get), patience from the drivers (if they can even summon more patience), and of course funds. I think people will initially reject the idea because its not exactly a desperate project, like say, the Replacement of the Eastern Span is. The geography willmake it even more expensive, some places you'll have to dig deep, others maybe not so much. But honestly, I would think that it makes much more sense to be able to maintain our surface road conditions before we start diving underground.
As for Transbay, I guess the two shorter towers could be built first. I've been thinking so much about the tallest one, I almost forgot about the shorter one (who would've ever thought I'd actually
forget about a roughly 1000 foot tower in SF!). I'm eager to see at least some preliminary renderings to Renzo's tower though, hopefully they annouce something about that at this meeting.