$53 billion train set

The Obama administration is asking for $53 billion over the next six years to pay for high speed rail, a far cry from China's $450-600 billion investment but still a considerable sum. A lot of time and energy has already been invested in planning out where high speed rail can do the most good, with this report being a prime example. (Others are opposed with equal vigor.) While the energy efficiency of trains is much higher than that of cars, there are a few issues that I've not heard well addressed. First, is there room for an additional or larger corridor for trains? Can the high speed rail supplant all existing slower trains, or can it somehow share tracks? Second, is the supporting infrastructure in place or at least economically feasible? In places like DC and New York, the subway system and buses are well developed, making it relatively easy for people to get to final destinations within the downtown area, at least, but in other places these are not as well established. Third, will systems be competitive? They have to provide dependable, inexpensive service that gets people where they want to go, and I have heard little about whether the systems will pay for themselves even accounting for positive externalities. I loved traveling by train in Japan, but I don't know if such a system fits this country's spacious dimensions well.