If the county does not own the fee simple title to land described by § 263.203 or 263.204 and if the owner of the fee simple has executed an easement to the land for the purposes for which a conveyance is authorized under § 263.203 or 263.204, the county judge, on order of the commissioners court, may join in and assent to the easement in the instrument granting the easement or in a separate instrument.