Ever Had A Horizontal Condo in Toronto?

Here's an interesting idea--take the extended backyards of older narrow-lot houses with back alleys, and build lowrise condos with underground parking (for both the houses and the condos) along the alley. You get a whole extra set of streets (presumably trash collection is curbside, not through the alley) and the equivalent of at least one granny flat per house. It wouldn't likely fly in most of the suburban US, where potential crowding is considered a bigger problem than sprawl, but it might at least get a polite hearing in Chirilagua.