Annexation to a city or town of all or a portion of a Cost Recovery Area shall not affect liability for pro rata reimbursement share charges of properties so annexed nor responsibilities of an Owner under the Cost Recovery Contract. If any property of the Owner is annexed by a city or town prior to completion of construction, all responsibility of the County with respect to portions of the property not constructed shall cease unless a supplemental contract/agreement is made with the annexing city or town assuring reimbursement of County funds expended on the construction of improvements.