What is the ruling if the purchaser and the pre-emptor (or his agent) both plant or build jointly on the undivided share before division?

Primary text

If the purchaser and the pre-emptor or his agent jointly planted or constructed on the undivided share, and then the pre-emptor claims the share, the ruling regarding his taking his portion of the resulting planting and construction is the same as the ruling established after a formal division (Muqasamah) has taken place.