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It's pretty difficult to get a placement if you're not bilingual, especially if you have a particular interest, like in the hospital/ health care system - you're expected to be able to communicate with clients, coworkers, police, government, etc. who only speak French or they don't want to talk to you in English.
Bilingual BSW students are allowed to do their final placement in hospital and I wouldn't even be considered. There are very limited opportunities for people who aren't bilingual - apparently this comes from the organizations and is coming down from the province. I did my BSW there and was told to either find my final placement in Cornwall and commute (2-3 days a week) or do a block placement in the spring/summer in Ontario (which would delay my graduation and affect my student loans). They don't want you finding your own placement in Montreal and wouldn't provide much help to find a placement or offer much supervision support if placement is done out of the area. Not sure how different the MSW program is, like if you can get set up to do a block placement elsewhere.
I consulted with people I knew who lived in Montreal and/or studied there before I went and general consensus was that I'd be ok in Montreal (especially downtown) as someone who isn't fully bilingual. I even know a couple Anglophone doctors who went to med school at McGill and they didn't have any issues with French. When I mentioned this to the placement coordinator, I was essentially told that med students and doctors are treated differently and "they can have other people translate for them".
Schools or programs tend to have a quota where they try to accept out of province students because they can charge them more for tuition. I paid for more tuition there and got little support. The majority of students were already from the Montreal area and they prioritize these people.
Just some food for thought based on my own experience...