(a) In any action, regardless of who is the moving party, where the boundary of land patented or otherwise granted by the state is in dispute, or the validity of any state patent or grant dated before 1950 is in dispute, all parties shall have the duty to disclose to all opposing parties all nonprivileged relevant written evidence then known and available, including evidence against interest, relating to the above issues.
(b) This evidence shall be disclosed within 120 days after the filing with the court of proof of service upon all named defendants. Thereafter, the parties shall have the continuing duty to make all subsequently discovered relevant and nonprivileged written evidence available to the opposing parties.