They're trying, or some close approximation there of. I know they're working on the east/west bit. I spent a chunk of the winter doing prep work on a few sections in the middle of the state with East Quabbin Valley Land Trust. There is an interactive map on the site where you can watch the progress.

This is the feasibility that MASSDOT did a while back. There are some sections that are already done, and some sections that are going to be an issue, either because the land is now privately owned, or it was developed and now they need to do a work around. It will be a few years, but we'll hopefully get there soon!

https://www.mass.gov/lists/mass-central-rail-trail-feasibility