There has been much confusion over Safeway's policy on using a BOGO coupon WITH their BOGO events. Many "coupon" sites have been giving misleading information, further frustrating store managers and Safeway...
Here is what they have posted with regard to their policy:

"You are able to use a BOGO Coupon on a BOGO Sale. We would like to clarify that a free item cannot result in a free item. In order to receive a free item from a BOGO purchase or transaction, one item must be physically purchased. If you apply a BOGO coupon to an item that is under a BOGO offer, you may receive an additional free item. However, the original item must still have been purchased (Example: Buy 1 Get 2 free with offer and coupon)." -Jessica, Customer Support


It is a good idea, if you haven't already, to check out their Facebook page for Canada Canada Safeway Facebook make sure you change "highlights" to "posts by others" so you can see FAQ's and answers