A city category would never be named with just the name of the city; it would always have the province/state or country in the name. For example, Category:Victoria, British Columbia. Only states/provinces and countries have just the name by itself. So, since there's no country called Victoria, and as far as I can tell the one in Australia is the only state or province called Victoria in the world, Category:Victoria would not be ambiguous.
~Lianne
