[OldDartmouthMark]

As far as the distance of rails ripped up, it's hard to say. Perhaps someone with more knowledge/familiarity with it than I can comment.

From Google maps, it looks like roughly 6 km from the south end rail cut to the old Fairview roundhouse, then there are multiple tracks for the switching yard. Then there's roughly another 12 km from Bedford to Windsor Junction, but I'm not sure how far up the double tracks went from there.