In 2004 CN decided to get into DPU aka Locotrol, well behind most RR's, especially CP who has been running distributed power for decades!
DPU equipped CN 2200-2205, were numbered separately from the rest of CN's Dash 9-44CW series (2500-2700). They were also restricted to Eastern Canada where DPU would be needed most.
Apparently CN liked DPU, since all new ES44AC's are equipped with it and CN has re-equipped a number of old Canadian cab Dash 9-44CW's in the 2500 seires.
Perhaps with more ES44AC's on the horizon, CN will start running DPU through Saskatchewan as well, making such sightings more common. Until then, you can only see DPU on CP potash trains, running literally behind the bushes in this photo (CP PNL runs parallel to the CN TRANSCON ~2 miles away)