Three teams of agencies representing WPP, IPG and Omnicom expect a decision this month in Cablevision Corp.’s Rainbow DBS review, following final presentations last month, sources said. Billings are estimated at $100 million. Each team is anchored by a New York ad agency. Omnicom’s team is lead by TBWA\Chiat\Day in New York, IPG’s by Lowe in New York and WPP’s by J. Walter Thompson in New York, sources said. The agencies either declined to comment or could not be reached.