You made me laugh here (and I don't even know if you're being sarcastic or not! :-) )
> YYZ-MTL corridor that all of the PMs except Harper (whom I dislike, but I digress) have hailed from
Joe Clark was from Alberta and Kim Campbell was from BC, though their stints as PM were too short to matter I guess. Diefenbaker was born in Ontario, but spent his childhood in and his electoral seats were from Saskatchewan. Robert Borden was from and represented Halifax.
I'm not disputing the presence of the "Laurentian Elite" or its (ill, IMO) influence, but proportionally to population the PMs haven't really been all that off regionally, especially as the population west of Ontario has only really grown in the last 30 years, especially in Alberta and BC.
>power is concentrated in the PM hands in a way unparalleled in the West
The UK would like a word. They've been lamenting the "presidentialisation" of the PM there since Thatcher took power.