Great news, Drydock!
Actually, the Governor General's Body Guard was not the only regular uniformed cavalry unit issued Winchester carbines for service in the 1885 Rebellion. The Winnipeg Cavalry Troop and the Cavalry School Corps (as the unit was then named ... it later became the Royal Canadian Dragoons) were also issued with the same configuration of Model 1876 Winchester carbines ... in my earlier post I only mentioned the GGBG specifically, because I happened to have a photograph. (I think my wording was something like "... regular cavalry units, such as the GGBG ...".
As documentary evidence, here is the actual tabular statement submitted by Deputy Adjutant General Lt.Col. W.H. Jackson, who was the Principal Supply, Pay and Transport Officer of the the Field force, outlining the "Arms and Ammunition Issued to Corps of the North West Forces, Settlers, and others", which formed part of the voluminous Report on the whole rebellion and the military expedition to quell it which was presented to Parliament in 1886. The units highlighted in yellow are the regular established and uniformed cavalry units issued with Winchesters ... other units also issued Winchesters (Dominion Land Surveyors Intelligence Corps, Moose Mountain Scouts, Rocky Mountain Rangers, Alberta Field Force) were non-uniformed provisional (i.e. temporary) militia units raised solely for the duration of the Rebellion.