I'm not sure about double exposure.
I will comment that the border adjustment accounts for emissions pricing in other countries. Canadian firms would just pay the difference between the headline rate in Canada and the EU's headline carbon price. The OBPS provides what I'll call protection.
Alternatively, in a counterfactual world where Canada does not have industrial emissions pricing, Canadian firms would face the full brunt of the EU CBAM, and the revenues would also go to the EU rather than be used within Canada.
