65 ILCS 5/7-1-37
After a part of a municipality is annexed to another municipality, both the annexed territory and the divided municipality shall have a right to service from any waterworks, gas, or electric light system, owned, prior to annexation, by the municipality that has been divided, on the same terms, that existed before annexation.
The annexed territory or the divided municipality may have its right terminated by the joint action of the corporate authorities of the annexing municipality and of the divided municipality. If they cannot agree, the question of termination shall be determined by the circuit court of the county within which the annexing municipality is situated, on the petition of any interested person. The court shall determine the question without a jury, and shall enter judgment as right and justice require. This judgment shall be appealable as in other civil cases.
65 ILCS 5/7-1-37