The short answer? Usually. Each event and venue may have different regulations but for the most part, if tickets are still available on torontoticketmarket.com, you should be able to buy tickets for that event.
Some notable exceptions are Broadway and classical music productions which tend to have very strict door and start time policies, music festivals which require physical tickets or wristbands to be mailed to you beforehand, some postseason sporting events like multi-session tournaments, and more.