Once a utility begins serving a customer, it gains an ongoing obligation to provide that service which it cannot abandon without specific authorization from the Public Service Commission. Approval to abandon is almost always contingent on service no longer being needed or wanted by the current customer and some additional circumstance that results in little likelihood future property owners would elect utility service either. As you can see, these factors can rarely be met, thus there is substantial precedent and case history to not allow a municipality to get out from under its obligation to continue an established service obligation. Abandonment would not be allowed as a tool to force customers outside of corporate boundaries to annex to the city.
Wis. Stat. 196.81 Abandonment; commission approval required.
(1) No public utility may abandon or discontinue any line or extension or service thereon without first securing the approval of the commission. In granting its approval, the commission may impose any term, condition or requirement it deems necessary to protect the public interest. If a public utility abandons or discontinues a line or extension or service thereon upon receiving commission approval, the public utility shall be deemed to have waived any objection to any term, condition or requirement imposed by the commission in granting the approval.