Any locality which is a member of a planning district commission may become a member of an additional planning district commission upon such terms and conditions as mutually agreed to by the locality and the additional planning district commission. The locality shall notify the Department of Housing and Community Development of its membership status in the additional planning district commission within thirty days of becoming a member. Whenever a state-directed activity is conducted by all the planning district commissions, the planning district boundaries identified by the Department of Housing and Community Development shall be used, unless alternative boundaries are agreed to by the localities and the planning district commissions affected. No additional state financial support shall be paid due to a locality becoming a member of an additional planning district commission.