If the proceeding is initiated by resolution of the city council and not by property owners, the notice described in subsection A above must be mailed to the owners of property abutting upon any part of a street or alley sought to be vacated, as shown on the rolls of the county treasurer, at least fifteen (15) days before the date fixed for the hearing; provided, that if fifty (50) percent of the abutting property owners file written objection to the proposed vacation with the city clerk, before the hearing, the city will not proceed with the resolution.