This just seems like a full time lobbying gig for elder statesmen (Ed Rendell! Tom Daschle! George Pataki! Christine Todd Whitman!) who don't know anything about trains. The cost of building something like this has little to do with the cost of the stuff the Japanese have offered to pay for. It's assembling necessary property and rights of way, and grading and tunneling where necessary, that's expensive.
Obviously it could happen, which is why you assemble a team of Washington Superfriends to help make it happen, but I'm pretty sure the most that will come out of this is a bunch of money wasted on lobbyists and consultants and reports and then nothing ever happens because it would be extremely difficult and expensive.
I'm not against shiny new technologies, but if you want to build something like this you build it between two cities that don't have much in between them. Also, too, flat helps. The NE corridor is extremely dense, so any project like this that can't make use of an exist ROW will be extremely complicated, expensive, and disruptive.
