Check out page 8 (Appendix B) for the provincial liquor tax rates that CBSA are supposed to apply (in addition to GST and PST):
http://cbsa-asfc.gc.ca/E/pub/cm/d2-3-6/d2-3-6-e.pdf
How much you pay for the excess wine above 1.5 liters thus depends in which province you will land in (I hope you're not landing at YUL as Québec has very high rates....

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