The real issue is that turbine powered trains need a fire hose to get fuel from the tank to the prime mover. The TurboTrain was a pre-embargo design, and I think the genesis of the Turboliner was also prior to that.
The idea of high speed trains without actual investment in the expensive infrastructure required for it (I.e. Electrification) is a temptress for those who don't understand the concept of TCO. Which is most Americans, a great deal of non Americans, and the entire legislative branch of this country. And most other countries, come to think of it.
Low-capital test shots like this are useful. For instance, use the machines 125 mph capavibility with a FRA waiver to demonstrate the value of a non-engine change, limited stop, 125 mph high speed service from Boston to Washington. Then use this validity to acquire the funds to electrify the entire line, acquire proper high speed sets, and run the real service.
The disadvantage is the financial watchdog morons that come pouring on to the scene like locusts discussing vaguely defined "waste", "expensiveness" and "unaffordabity". I define waste as "using time for listening to financial watchdogs", "expensiveness" as "the cost of lost oppurtunuty for projects financial watchdogs delay" and "unaffordibility" as "not affording building a wasteful and expensive large container to seal financial watchdogs in and dump into the ocean". But that's me.