Burial records including pictures of most headstones from Montreal cemeteries are online at JOWBR (reached through JewishGen).
You can also do research at JGS-Montreal.org. (Scroll to the bottom -<Research>-and click on Dashboard for links for numerous sites.)
Most (Jewish) burials in Montreal are handled by Paperman. I don’t know about now but in the past they sent me the Burial records that listed all the information about the deceased. They would have prepared this information to send to the government for the preparation of official death certificates.
You might be able to find what you need this way. But if you need official documentation the government of Quebec website is www.gouv.qc.ca.
Judy Winstan Brandspigel
Montreal, Que. Canada