i think between MD and DC is feasible, and actually would be the exact economic stimulus MD needs. it makes sense to invest in a system like that which would add value to a city by attracting well-to-do commuters.
if they can keep the daily costs of the commute relatively low for users, then it has some real potential.
the issue with New England is that there really is no room for new tracks around here, especially around Boston. we've done a good job of letting our rail system disintegrate into crap. the remaining peice that still function are in need of repair or replacement. there are some corridors that might work through less populated areas: Boston to Portland, ME; Boston to Providence, RI; and Boston to Worcester, MA. but after our $14B spending spree on the Big Dig, i doubt the feds would give us any more money on transportation improvements.
