CNA Insurance Co. had a clever justification for declining to defend a policyholder that was sued in hundreds of asbestos cases. But it had to persuade the Illinois Appellate Court to extend the line of cases that permit judges — in “certain circumstances” — “to look beyond the allegations of the underlying complaint to determine if the duty to defend has been triggered.”From June 1, 1974, to June 1, 1980, three CNA subsidiaries — Continental Insurance Co., Continental Casualty Co. and Transportation Insurance Co …