The Ottawa Citizen has a good story, with a bit of the history, about the parkade. It seems that I was wrong about when it was built. I had used GeoOttawa and seen the garage in what I thought was 1976, but it was just a ‘ghost’ of the 1991 image. The structure was built in 1989, so it is about 36 years old.
https://ottawacitizen.com/news/clean...arage-collapse
According to the article, the land was owned by the City of Ottawa before it was given to developer Aron/Olympia York on the condition that they build at least 500 parking spaces. They built this 400-space garage.