Admissions at universities in Canada tends to be predictable for local students, and students from Quebec generally have quite a good idea what grades are needed to get into McGill. This means that McGill has a lot of applicants who are academically quite strong, and not so many applicants that are not going to get in simply because the local students mostly don’t apply if they are not likely to get in. This suggests that it is possible to be quite competitive for admissions, and yet still have an acceptance rate in the 40-50% range.
McGill has a sort of rolling admissions, where acceptances are sent out over time. As such it is difficult to predict when you will hear back.
McGill does admit by major, or at least by which faculty you are applying to. What grades will be needed will depend upon what your major is. My vague recollection is that the Faculty of Arts is slightly easier compared to computer science and engineering, which should help you.
Admissions at McGill is very heavily dependent upon grades, and yours appear to be very good.
I think that your chances are very good.
You could hear back any time from December (less likely) to February (more likely) to mid April (less likely unless you are very close to the cutoff).