FYI, the federal standard in the United States is that motorcycles are allowed to use HOV lanes.
(Yes, I know this thread covers Toronto, but some of you may want to know the situation to the south.)
Here is the situation, according to
http://ops.fhwa.dot.gov/freewaymgmt/faq.htm#faq15
Why are motorcycles allowed in some HOV lanes?
Motorcycles are permitted by federal law to use HOV lanes, even with only one passenger. The rationale behind allowing motorcycles to use HOV lanes is that it is safer to keep two-wheeled vehicles moving than to have them travel in start-and-stop traffic conditions. States can choose to override this provision of federal law, if they determine that safety is at risk.
What this means to me is that every motorcycle can use every HOV lane in the USA, except lanes where a state has chosen to erect a sign prohibiting motorcycles. Specifically, I do not much like riding on I-77 through Charlotte NC, but I sometimes do it. OK, there is a HOV lane through most of the city, and I prefer to use every inch of it in both directions. You are welcome to do the same, or not, as you choose.