75 ILCS 16/10-55
When the employees of a public tax supported library of a county, municipality, or township are participating in an employer provided Illinois Municipal Retirement Fund or other retirement or pension program and the library is converting to a library district under this Article, the corporate authority shall continue to provide coverage under the retirement or pension program until the newly established district library provides retirement or pension program coverage. In no case, however, shall the corporate authority extend its coverage for more than 547 days after the effective date of the circuit court's final order of establishment. Any payments made by the corporate authority for coverage shall be reimbursed by the district library.
75 ILCS 16/10-55