I don't know of a single calling card that is sold in Montreal that doesn't work in the 450 or 514 area code.
I suggest that the next time you come to Montreal, you just go to almost any corner store (called depanneur) and buy one of these cards. They will work and most of them even have a 1-800 number that you can call if you there isn't a local number for the city that you are currently in.
I once brought my calling card to NYC and was calling Montreal by just calling the toll free number and then keying in the PIN and the Montreal number that I wanted to reach.
The 2 things that you have to take a note of when buying these cards is whether the cards charge a monthly maintenance fee regardless of whether you use the card or not from the first day that you use it and whether there is any (and what) the connection charge is.
The connection charge is important since regardless of whether you speak with the person or not, the connection charge will be removed from your calling card. So if you find a card where the connection charge is $1.00 and for North American calls and charges you $0.005 per minute, if you call someone and get their answering machine (or voice mail) and hang up, your $1.01 will be deducted from your card.
Also, using the toll free number to initiate a call as opposed to a local number carries a surcharge.
I hope that this helps.
