The Canadian competent authority generally will grant an S corp agreement

Dual resident individual shareholders of an S Corp can apply to the Canadian competent authority under Art. XIX, para. 5 of the Canada-U.S. Treaty for an agreement to have the S Corp treated for Canadian purposes as a controlled foreign affiliate earning foreign accrual property income. This permits the Canadian and US income to be synchronized so as to avoid loss of Canadian foreign tax credits.

By implication, the competent authority generally will grant the request as a matter of course unless "the shareholder does not submit the information requested by a competent authority or the Canadian shareholder is seeking to revise his Canadian tax reporting for past years." It is acceptable (although not encouraged) for the shareholder to request an S Corporation agreement and then file the Canadian returns in the expectation that an S Corporation agreement ultimately will be provided.

Neal Armstrong. Summary of 19 September 2015 STEP Roundtable, Q.4 under Treaties – Art. 29.