I just realized I wasted the above reply on a person who isn't even in law school yet. Let's take a step back even further and get some perspective. Please, please, please do not be one of those assholes in law school who imagines that large, Bay Street firms represents the "big leagues" in some sense, where all the best people go, and everyone else who can't hack it settles for something else. Please, do not be that person. There is so much about the legal marketplace you don't know, aren't expected to know, and so many possible avenues of interest for you out there.
One of the reason so many lawyers in large firms are unhappy isn't because the work is inherently bad of soul-crushing. It's simply because they followed the most obvious path, bought into a lot of the myths lurking behind your questions, and simply grabbed what they thought they were supposed to aim for rather than spending any time at all actually evaluating and pursuing their genuine interests. Take the many opportunities you'll find in law school to figure out what actually interests you. Do not base your future career on what looked cool in television.
Ontario has its high profile work. For example, I'm sure that PST, OKT and a bunch of Bay St firms are all involved in this: