I seem to recall during the original CAN - US FTA negotiations that vintners across Canada were saying they'd be wiped out by the Napa Valley growers.  However, the smart ones looked further ahead, invested and grew their businesses, and from what I can see we have a pretty healthy domestic wine industry.
So for any amount of US-originating milk/cheese, why not country of orgin labeling or a warning that it may contain BGH ?