It is not clear how these are being sent, but users are reporting finding $10 off when you spend $30 gift card looking coupons in the mail.  So far, they have been received in Ontario and British Columbia.

Limit of one $10 Montana’s Card redeemable with minimum purchase of $30 (excluding alcoholic beverages and taxes). One $10 Montana’s Card per table. Must present original $10 Montana’s Card. No cash value. Valid Sunday to Thursday only, except Sunday, May 12th 2013. Valid at participating locations. Cannot be used with any other offers. $10 Montana’s Card is redeemable until May 30th 2013.

Thanks for the information kristeven. Click here for the discussion thread about this deal