I'm sorry, I'm not quite sure I place the line in Wakefield that you are talking about.
However, I love abandoned lines (well, obviously I don't like them being abandoned). I'm in B&M territory as well. My closest abandoned lines are the Maynard Branch that began in South Acton and the old NH Framingham and Lowell in North Acton.
After hearing about the Maynard branch, I wanted to see how much is left. While at SA station about a year ago, I searched for clues of its existance. Underneath the thick brush and leaves (This was November) I saw an old switch on the line. The switch (presumably for a spur) and the rest of the maynard branch have been cut off from the main by the Rte 27 approach to the new bridge over the main. I also saw an old telltale without the hanging rope that warns brakemen, just a big metal bar to throw them off the roof
. I believe that this telltale was for the water tower that stood at the edge of the branch. I haven't gotten the chance to walk the old line, and I didn't really feel like walking on a muddy portion of the line with nobody there around me and with no bike lock for my bike (No way to get my bike down to the tracks).
The old F&L ended service about 6 years ago with the termination of service to a lumberyard in North Acton (the name is escaping me now). The line was run by the Bay Colony using a 44 tonner. The real scene was in East Acton where trains had to be flagged across a 4 lane, high-speed Route 2 with sloping sides that would initially make visibilty worse as well as braking distance longer for oncoming vehicles. I wouldn't want to be a conductor on this train! The old line is still intact. Starting north from W. Concord, the old diamond can be seen paved in brick between the F&L and the Fitchburg. While there is a bridge out between W. Concord and the State Prison, its easy to pick the line back up where Commonwealth crosses it beside the prison. Later, the line passes through some nice farmland, and the line can be seen from (and is crossed by) route 2. After that, the line is pretty nice and is preserved, passing through some nice farmland, woods, and past alongside a brook (again, the name is escaping me). I cross this line very often in my regular activities on trips to N. Acton. Most roads that it crosses have no remaining protection from before. Rte 2A has some decrepit flashers. However, I think there is a shed there that may be a NH vestige. I need to check it out, it might be a well.
Later, it parallels Rte 27 for quite a while, so it pays to take Rte 27 from Acton to Maine Trains in Chelmsford.
Well, unnecessarily long narrative...but...well...