Pretty hard to do
We lived onboard over a couple of winters in New York City and being in the water helps a lot since it is not much below 30F (salt) and the air near the surface is kept a bit warmer too. On the hard the boat would be exposed on all sides to air that could be -20 and colder. Don't know if people live on boats all year in Montreal - there are lots of people doing that in Toronto which is similar in terms of weather (other than snowfall).
Back in the water in Grenada - with new main and #2 and cockpit canvas (Santa came early). Will spend the winter and early spring in the Caribbean and then head to Bermuda and the northeast US. Still trying to decide if we will bring the boat to Canada, either in 2015 or 2016.