Before you letter it "MOW", just recognize those cranes didn't belong to the "MOW" department.
MOW = maintenance of way, the engineering department that repairs the track. Wrecking cranes like that belonged to the Mechanical department, the same guys that run the car shops, RIP tracks and engine facilities. Traditionally there are 3 departments on a railroad: Operating/transportation (train crews, clerks), Engineering (track, bridge and signals), and Mechanical (cars and locomotives).
MOW did have cranes but they had conventional booms, generally lower capacity and were designed to do bridge and track maintenance/construction). Wrecking cranes are designed and equipped to pick up cars and locomotives. Occasionally the MOW department would borrow a wrecker to change out a bridge section or lay track panels, but the Mechanical department almost never borrowed a MOW crane to pick up a car and wouldn't have the capacity to pick up a locomotive.