11. (1) The city council and the county council may, before the transfer day, make an agreement providing for—

(a) the continued vesting in the county council on and after the transfer day of any land situated in the relevant area that, upon the making of the agreement, vested in the county council,

(b) the joint ownership by the city council and the county council on and after the transfer day of any such land, or

(c) the use by the city council and the county council of any such land or any land standing vested in the city council by virtue of section 9.

(2) An agreement under this section may contain such incidental, supplementary and consequential provisions as the city council and the county council reasonably consider necessary for the purposes of the agreement.