You can download geospatial data for Montreal from the Harvard Geospatial Library: hgl.harvard.edu. I don’t know exactly what kind of data you are looking for, but you might find data by DMTI Spatial useful. You can also look at geobase.ca, where you can download free geospatial data for Canada.
Feel free to drop by the library if you have any more questions on geospatial data resources.
