Notwithstanding paragraph (3) of subdivision (a) of Section 2804, this division applies to proceedings where a petition is signed by an owner of 40 percent or more in area of the property proposed to be subject to assessment, and where some or all of the other lots or parcels proposed to be subject to assessment are used primarily for residential purposes, unless the petition and waiver is also signed by owners of 50 percent in area of the property proposed to be subject to assessment which is not owned by the owner of 40 percent or more in area of the property proposed to be subject to assessment.