The "Travelers Guide to the Firearm Laws of the 50 States" says "Canada prohibits the importation of any handgun without an Authorization to Transport (ATT). These ATTs are rarely issued to Americans and are given to Canadiens on a highly discretionary basis. Travelers without an ATT who attempt to enter Canada with handguns will have their weapons confiscated, their vehicles impounded and could face prosecution. Securely casing the handgun and stowing it in the trunk will not prevent seizure. Mere possession of a handgun anywhere in a vehicle without an ATT is illegal."
Pretty much sums it up.
You can try calling the Canadian authorities @ 800-731-4000 to try to get an ATT, but don't hold your breath.