There would obviously have to be a redevelopment plan and some properties bought up for the ROW. Gardenvale Road runs roughly from McArthur to the Aviation Parkway near La Cité Collegiale.
As for the bridge across the Rideau, Cummings Bridge could be redone with a wider upper deck for traffic and a narrower lower deck for transit (like a mini Bloor-Danforth Bridge in Toronto), or a tram-specific bridge (plus ped and bike) could be built to Laurier and run trams there. In fact, once most of the buses are gone from Albert/Slater after the Confederation line is built, the segregated bike lanes could be moved there and Laurier could become a downtown surface tram ROW with some sort of eventual connection to Carling
THere could also be s spur at the NRC up to the Rockcliffe Base site