TTAC3 - run by Brian McIlmoyle whose on the forums, CQB max 20 players but usually less. Games typically on Fridays.
Paintball CQB - Eco usually hosts games there, they got an indoor and outdoor venue right across from each other. Player cap is usually 30, sometimes higher. They usually play Sundays.
Defcon - they have 2 locations, one is indoors in Scarbrough, the other outdoor area is just north of downtown Toronto. Able1 is usually the host. I've yet to go either venue but I usually see game posts for Sundays, sometimes Tuesdays.
You would have to keep an eye out on the Games and Events Schedule in Ontario on the forums to see where and when games run and PM the host(s) to see if they'll allow you to spectate and DO NOT ARGUE WITH THEM, remember that its their party so they have final say.
"Hey I'm the first one to say its a great country but its a straaaaange culture. This is a place where gun store owners are given a list of stolen credit cards but not a list of CRIMINALS and MANIACS. And now they're thinking of banning toy guns...AND THEY'RE GONNA KEEP THE F**KING REAL ONES!"
-George Carlin 1937 - 2008 (RIP buddy)