CRA considers that the HST/GST customs release rule can apply only where the related sales agreement was entered into after importation

On its face, ETA s. 144 deems any supply of goods which otherwise would be deemed to be made in Canada by a registrant (including a registered non-resident) on the basis of the legal delivery occurring in Canada, to instead to be made outside Canada if the goods have been imported and their legal delivery (e.g., DDU or DAP destination) occurs before customs release.  However, CRA considers that this rule does not apply where an agreement for the supply of the goods was entered into before the goods are imported  - so that s. 144 has only a narrow field of application.

Neal Armstrong.  Summary of CBAO National Commodity Tax, Customs and Trade Section – 2014 GST/HST Questions for Revenue Canada, Q. 33 under ETA, s. 144.