Mont. Code § 67-2-503
The reports of investigations or hearings may not be admitted in evidence or used for any purpose in any suit, action, or proceedings growing out of a matter referred to in the investigation, hearing, or report, except in case of criminal or other proceedings instituted in behalf of the department or this state under this title and other laws of this state relating to aeronautics. An officer or employee of the department may not be required to testify to any facts ascertained in or information gained by reason of the officer's or employee's official capacity or be required to testify as an expert witness in a suit, action, or proceeding involving an aircraft. The department may, in its discretion, make available to appropriate federal and state agencies information and material developed in the course of its hearings and investigations.
§ 67-2-503, MCA