 NEW YORK--BUSINESS WIRE--Ambac Financial Group, Inc. NYSE: AMBC Ambac, a financial services holding company, today announced that it has launched Everspan Group, a specialty, participatory fronting program insurance business. Earlier today, A.M. Best issued a Financial Strength Rating FSR of A- Excellent for Everspan Groups core insurance companies, Everspan Indemnity Insurance Company, an excess and surplus lines insurer and Everspan Insurance Company, an admitted carrier. Wit 