The B&E is a Genesee and Wyoming operation that operates the former Boston and Maine route that became the Pan Am Southern when NS and Pan Am Railways created the partnership and the 50-50 split ownership of the route between Ayer, MA and Mechanicville, NY.
As part of the sale to CSX, CSX had to divest itself from this route due to a conflict of interest when they purchased Pan Am Railways because they already operate a similar route in the region between Selkirk, NY and Boston. It's been rumored that the B&E will become the operator of this line once CSX sells its portion of PAS because they have no interest in operating this redundant line.