London-based Royal & SunAlliance Insurance Group scored a victory Tuesday when a state court in Michigan said General Motors Corp.’s efforts to seek coverage for its asbestos and environmental liabilities are time-barred. Judge John J. McDonald of the 6th Circuit Court in Pontiac, Mich., granted a pretrial motion by Royal & SunAlliance USA, RSA’s U.S. operation, for summary dismissal of the case. A coverage trial had been expected to be held within the next few months.