"Despite growing production at home, the United States imported eight million barrels a day of crude on average last year, with 3.3 million barrels a day – or 40 per cent – originating in Canada. Virtually all Canadian crude exports go to the United States.

Mr. Verleger said either a border-adjustment tax or a crude-import tax would hit the Canadian industry hard, forcing producers to discount their prices to remain competitive in the U.S. market" 

I think I'm missing something here. Canada would only be at a competitive disadvantage if US needs could be met entirely by domestic production and Canadian producers were forced to compete in the US market place. Since the US doesn't produce enough it has to import. Slapping on a border adjustment tax would hit all oil imports equally which would only serve to drive up the cost of oil in the US. There would be no reason for Canadian producers to reduce pricing to offset the cost of the border adjustment tax, the US needs the oil.