Two of Canada's blue-chip law firms, Fraser Milner of Toronto and Byers Casgrain of Montreal, are in serious merger talks, legal sources said yesterday. Fraser Milner was created about a year ago in a merger of Fraser Beatty and Fenerty Milner. At the time, the newly formed firm said its goal was to become a national player. Byers Casgrain has been in play since its association with Toronto's McMillan Binch and Vancouver-based Bull Housser dissolved about two months ago. Fraser Milner has about 350 lawyers in offices in Vancouver, Calgary, Edmonton, Ottawa and Toronto. With the additional 100 Byers Casgrain staffers in Montreal, the merged company would rank among the five largest law firms in Canada, by employees.