If the number is an 800 number it will be good in Canada.
If you think your connection is tight, try to figure out what options are available in Montreal so that you can direct them to your preferred backup plan. Also, do not forget that the airline will also be looking to rebook you if the connection is missed. Depending where you are flying to it’s likely there are other flights later that you can be rebooked on (assuming there are seats).
In closing, it’s always important to select a connection time you are comfortable with even if a shorter connection time is legally allowed.