Massachusetts has asked for federal funding to build a third track along part of the NEC in Massachusetts (Readville to Canton Junction, I think); I don't remember exactly which program they've asked for that money from.
The justification for that track has been Fall River / New Bedford commuter rail service.
There is some question as to how cost effective Fall River / New Bedford commuter rail service will be; there are concerns about how long the travel time to downtown Boston will be; it is likely that Fall River / New Bedford will see far fewer trains than a Blue Line extension to Lynn would; and there seems to be NIMBYism along every possible route that has been considered.
I believe that even if Fall River / New Bedford commuter rail service never happens, a third track from Readville to Canton Junction has the potential to enable express commuter trains that make 8-10 stops in Rhode Island, and very few stops in Massachusetts, which would help to get more of Rhode Island within a 90 minute train commute of Boston's South Station.
My question is: if a third track from Readville to Canton Junction gets built with a Fall River / New Bedford justification, and ends up being used for express Rhode Island commuter rail instead of Fall River / New Bedford service, is the federal government going to come looking to get their money back?