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Around Winnipeg they are mainly used in hump service on the CN but a few escape to help with switching around the city as well. You see them on the mainline being transferred from time to time.
The CP has powered units with slug mates stationed not far from here in Selkirk for the steel mill run.
The CN slugs always run with 7200 series GP9Rm units which are set up as slug mothers. (There are also some 7500 series GP38-2s, but those are exclusively hump units.)
These GP9/slug sets are used in yard switching, and not for road service. A road local might use a set of 4000-4100 series GP9Rm, or just about any other piece of equipment CN has lying around.