Yes I know of those tracks, by the power distrobution thing, im talking about the bridge right off 1A that goes into chelsea, by the MWRA(i think?) sewage pumping plant..
http://maps.google.com/maps?q=1+eastern ... &t=k&hl=en
Not the best, but that bridge, the green one, (not the drawbridge on meridian st)...
2 days ago coming over that bridge I hit the track, went from aspault (sp?) to like a cobblestone w/ a track in it, just one bar, im assuming it is for rail, due to the fact that there is alot of track nearby!
Tho yes, the other tracks are elusive, those are strange, go all through East Boston, then meets up with the CR tracks from chelsea, which at the beginning, they are cut off now, due to the rehab project there doing by airport station w/ the ymca and park, and the bike trail that was further up!