That always struck me as kind of a fly-by-night operation. There's a long thread about the situation here:

https://railroad.net/boston-surface-railroad-worcester-providence-commuter-rail-t160242-750.html

As one commenter mentions the odds may have been better back when the Providence & Worcester was an independent locally-owned operation. But they got acquired by the Genesee & Wyoming which is a huge international RR holding company conglomerate and I expect they're not interested in sharing their right-of-way for anything less than serious $$$ up front.

In the ideal it seems like it would be a good route for DMUs, or perhaps even BMUs, someday. But not sure if the US regulations with respect to operating lightweight units on the same tracks as freight have changed, yet..the FL9 is a museum piece, hope some good Samaritans save it before it rusts away completely.