There is an old railroad bed from Ashburnham, MA and runs north to Troy, NH. I know the M&M crosses the r.r. bed in the center of Troy. I am not sure where it crosses the Mid-State. That may be an option. Used to mt bike and x/c ski on parts of it. I know for a fact that some of the land was purchased (as in Winchendon, MA) but can easily be by-passed. Does go thru the center of Winchendon, Troy and Fitzwilliam Depot. Again not sure where in Ashburnham.
note: I have not been on these for 6+ years. Check snowmobile trail maps for the area.