Section 51292 shall be enforceable only by mandamus proceedings by the local governing body administering the agricultural preserve or the Director of Conservation. However, as applied to condemnors whose determination of necessity is not conclusive by statute, evidence as to the compliance of the condemnor with Section 51292 shall be admissible on motion of any of the parties in any action otherwise authorized to be brought by the landowner or in any action against the landowner.