That kind of zone here (NCx, Neighbourhood Commercial and GCx, General Commerical) allow residential uses, in the case of a NC2 and GCx, however, at least 50% of the building's floor area must be devoted to commercial uses. (On my street, most of these have vacant ground levels.) This allows a store to have apartments above and below it, or in many cases here, a house to have a commercial space on its main floor while the family lives in the rest of the building. (That is, the store is just a room of their house.) I think all of our residential zones also allow limit commercial uses within certain development parameters as well. Hamilton must have similar zone restrictions.
Site plans don't have blocks with different zoning here, but different restrictions (within the guidelines of the zone) can exist on the same lot with the same zone class. An apartment complex to be debated next month will be all zoned RM2 (medium density apartments) but half of the lot will only allow apartment blocks, and half will only allow townhouses. If a place has a different zone, it is a different lot, but it can be owned by the same owner as the one next door and "blend" into the development. (Our Superstore is on about 200 small lots that were originally zoned for houses--apparently that was easier than combining them all into a single lot; and Victoriaville, our downtown mall, is a single building on a variety of lots, its hallways are zoned as streets and the buildings are zoned as Central Business District.)
Bureaucracy.