Any person may submit a redevelopment plan to an authority, or an authority may consider a redevelopment plan on its own initiative. An authority shall immediately transmit the plan to the planning agency of the city in which the area to be redeveloped is situated, for its study, or, if no planning agency exists, the plan shall be submitted to an agency indicated by the governing body of the city. An authority shall request the written opinion of the planning or other agency on all redevelopment plans submitted to it prior to approving those redevelopment plans, and the planning or other agency shall submit its written opinion within 30 days.