In Ontario, at least, the provincial government might have to step in and limit the difference between residential and commercial tax assessments. However, if Toronto were forced to lower the difference between residential and commercial tax levies to put the commercial levy at the same degree higher as the neighboring municipalities do, the tax burden on Toronto residential would have to rise a lot, which in turn would cause a lot of political upheaval. Since the majority of homeowners tend to vote in municipal elections (most tenants don't), that would pose a big problem for local politicians.