The B&M cab signal territory extended from West Cambridge to East Deerfield. While my memory may be a little hazy after 50 years I want to say that it was discontinued in the late 1960s because that's when the two pairs of Fitchburg Division freights that used foreign runthrough power (the Bow coal trains and Boston-Chicago piggybackers PB-99 and PB-100) stopped being led by a B&M GP9 as had been required for cab signal purposes.