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I don't know and these cities in Ontario also isn't sure.
According to City of Toronto, the regulation that little residence know is no one over the age of 14 is allowed on a bike on sidewalk. Most people still think it is the old rule which hardly anyone really paid attention to anyways about wheel size over 24 inches is not allowed. (And there are still lots of web pages stating that is the rule)
City of Markham to the north however is allowing sharing of sidewalk between bikes and pedestrians.
So on the division street (Steels Ave. ) between the two cities you have 1 set of rules that say yes on the north side and no on the south side for a cyclist over age of 14.
Interesting eh?
Build more bike lanes. Provide more training to improve cyclist ability. Put some bike Nazis out there to get the unsafe bikes off the road especially those with no light/reflector at night. If City council tried a electronic disposal tax they can put a bike infrastructure tax on every bike sales and services to fund bike friendly / safety changes.