Does your program have a co-op/internship requirement? If not, you won't be able to get the letter for the work permit.If I apply for coop work permit now, can I start work while waiting for the result?
It's hard to give you advice about whether summer is a scheduled break or not because it's really up to your department. My situation is very similar to yours (MEng at UofT, by the way), and it's not considered a scheduled break. Other than that, we can't really tell you it's one way or the other, unfortunately.