The redevelopment plan for a project area which is merged pursuant to Section 33470 shall be amended in the same manner as other redevelopment plans are amended. Notice of the public hearing shall be mailed to the last known assessee of each parcel of land not owned by the agency within the boundaries of the project area described in the redevelopment plan being amended. Notice of the public hearing need not be mailed to assessees of parcels of land within the boundaries of other project areas combined into a merged project area pursuant to Section 33470, except that notice of the public hearing shall be given to the project area committee for each project area which is part of the merged project area.