The state should not subsidize business period. Corporate welfare is costs about $150 billion a year according the folks who have tallied up the tax breaks and subsidies that corporations receive.
High speed rail is a beautiful thing. I went from London to Paris is three hours flat on the Chunnel train. No hassle of getting to the airport, no crappy airline food, a great view of the countryside at 150 mph, no traffic jams to worry about.
Another consideration: we are running out of radio frequencies for communication with aircraft. When we do run out of frequencies, airlines won't be able to put additional planes to work, which creates a window of opportunity for high speed rail.
I suspect the frequency issue could be solved much more quickly and cheaply than by building high speed rail.