Ill. Admin. Code tit. 83, § 470.100
a) Upon request of a Governmental Aggregator and receipt of a verification from the Governmental Aggregator that either an ordinance has been adopted authorizing an Opt-in Aggregation Program, pursuant to Section 1-92 of the IPA Act, or an ordinance has been adopted and a referendum passed authorizing an Opt-out Aggregation Program, pursuant to Section 1-92 of the IPA Act, the electric utility shall provide the information required in this subsection. If, however, the Governmental Aggregator is a township board, then the electric utility's obligation to provide customer account numbers is contingent upon the township board first providing an accurate customer list to the electric utility. The electric utility shall provide to the Governmental Aggregator, in electronic format, the following: