Health insurers have made an enticing pitch to local governments across the country: When your workers see doctors outside your health plan's network, costs can balloon, but we offer a program to protect against outrageous bills. Cities, counties and school districts have signed up, hoping to control the costs of their medical benefits. Then come the fees. Behind the fees is a little-known partnership between major insurers — including UnitedHealthcare, Cigna, Aetna and Elevance Health — and a data analytics firm called MultiPlan.