Between them, Envision and TeamHealth, owned by the private equity firm Blackstone, control at least one-third of U.S. hospital emergency departments. The suit, filed in California state court, does not seek monetary damages. It asks the court to stop Envision from operating at Placentia-Linda and other hospitals in California, where the suit says it staffs at least a dozen emergency departments. Before Envision took over the contract to run the emergency department at the Placentia hospital, an AAEM group staffed the department. Envision and KKR declined to comment on the lawsuit.