CN used these unique units to replace 2-6-0 or 4-6-0 steam locomotives on light-rail branch lines in eastern Canada.
This was largely the result of a very short rear hood housing the electrical cabinet, whereas they were located in the long hood on most road switcher designs.
To make the locomotives suitable for weight-restricted light rail branch lines, MLW spread the weight over the rail surface using A1A-A1A trucks (3 axle trucks, with the center axle of each truck unpowered) that had been manufactured by Dominion Foundries and Steel (DOFASCO); this same truck was also adopted for the MLW RSC-13.
Less weight on the powered axles resulted in less traction, hence the need to de-rate the engine horsepower to 1,400 hp (1,040 kW) to preclude wheel slippage.
The remaining three units found their way to the South Shore of Nova Scotia toward the end of their career by the late 1960s, and their domain extended throughout CN's former Halifax and Southwestern Railway system.