FYI, In the event that you arrive late at the export office or on the weekend at Lewiston, US customs will allow you to drive the vehicle legally into Canada for the duration of the weekend but you must return Monday WITH the vehicle to get your original title cleared by a customs official.

They will need to visually see the vehicle on the property from the office window. If you use another vehicle to drive down you'll be forced to go back into hoserland to retrieve the exported vehicle.