While some cities allow the construction of "garden suites" or accessory units on a case-by-case basis, Vancouver, BC is permitting them on any lot that is sufficiently wide and has access to a back lane:
"Vancouver... introduced a new policy a year ago that allows small houses to be built behind any single-family house in the city that has a lot wider than 33 feet as well as access to a lane or road. So far, nearly 200 applications have come in – a number that has made Vancouver a North American leader in enthusiasm for this new form of housing.
That all-out charge forward in Vancouver has produced backlash, though. At council meetings two weeks ago, when planners brought up an assessment of the program so far and suggestions for minor tweaks, 35 people showed up and about half were adamantly opposed, saying the new houses are so big that they're invading neighbours' privacy and blocking views."