I'm a Canadian and graduated this year with an honors degree in a field in humanities and an average of 4.0 in my last two years. I would like to stay in Canada for an MLS but have no idea where I can find information about which university is better at teaching which specialization
I'm not sure what you mean be which universities are better at teaching a specialization. If they have a specialization, there ought to be sufficient qualified faculty there to teach it. You're probably not going to find 5-10 courses in a 'specialty' they way you would see a lot of courses for a major as an undergrad. You may find only 1 or 2 courses in a specialty and you'd have to find a job or internship to gain the practical skills associated with it.
I'm in the US and can't speak for Canadian schools, but I know people at Toronto and UBC. If you're interested in archives, UBC might be the better bet. Toronto seems very cutting edge to me and has some internationally-known researchers.
4. Will I be at a disadvantage of being admitted into a program if I didn't have any work experience in a library setting?
No. We admit people every year who haven't done anything more than take out a library card and borrow a book. What we're more interested in is people who are open to changes in the field (it's not all about the book) and who aren't afraid of technology. You will have the opportunity to learn various technologies in school; don't shy away from it.
You also need to want to interact with people. Many applicants give the impression that all they want to do is hang around the stacks. Well, that's not the job. As an academic librarian you may teach literacy to incoming freshpeeps. In a public library, anyone can come in and you'll have to deal with all kinds of people and their problems. In some jobs (especially in a big academic library), you may not have as much public contact as other library jobs, but you will be dealing with vendors or professors across campus. If not required by your program, you would be well-advised to take a management course.
I don't know if this is true in Canada, but in the US, you really need some kind of library experience to be competitive on the market. You can get this experience in school, either a PT job, interning, volunteering even, but you have to have seen the inside of an information organization. My students who work full time in other fields and graduate without library experience have a MUCH more difficult time finding a job than those who were active while students.
I can't say whether it's easy or difficulty to switch between public and academic librarian. Maybe one of the practitioners will chime in on that.