Sorry, showing up late to this thread, so don't take these as direct replies so much as springboards for my points.
Counterpoint is that Yonge and Eglinton can be generally defined as midtown, and including St Clair. Summerhill is a grey boundary IMO.
Summerhill has long been contemplated as a relief station for Union, has it not? l I also reject the notions that GO trains through Summerhill and other spots along North Toronto / Belleville subs are merely 'interesting' or that it isn't something we can't be serious about.
Agreed, but I can see a link between frequent users of high speed rail to Ottawa and the Summerhill area, but that's a crass sentiment on my part.