MONTREAL — Paul Atkinson, CEO of digital media company Casero, has become chair of the board of the Toronto Intl. Film Festival Group, it was announced Thursday. Former chair Allen Karp will remain on the board.The board has elected helmer Deepa Mehta, William J. Fox, Warren Spitz and Constance Sugiyama to replace four members who have resigned. Fox is executive veepee at Bell Canada, Spitz is CEO of UCS Forest Group and Sugiyama is senior partner at Gowling Lafleur Henderson.