TORONTO, Dec 6 (Reuters) - Canada's main stock index opened higher on Thursday, led by a 25-percent jump in Loblaw Cos Ltd after Canada's No. 1 grocer revealed plans to create one of the country's largest real estate investment trusts. The Toronto Stock Exchange's S&P/TSX composite index was up 16.04 points, or 0.13 percent, at 12,173.33 shortly after the open.