When Berkeley became the first city in the nation in November to impose a soda tax, boosters predicted it would spawn copycat tax drives throughout the U.S. But detractors, led by the American Beverage Association, said quirky Berkeley is too far outside the mainstream to set a national trend. Who's right? A partial answer appeared to be bubbling up, not from a U.S. city, but north of the border, where a Montreal City councilman announced he would introduce a proposal Dec. 15 to tax boissons gazeuses sucrees to combat diabetes and obesity.