Mont. Code Ann. § 39-71-517

In pursuing remedies under 39-71-501, 39-71-503 through 39-71-511, and 39-71-515 through 39-71-520, an injured employee or the employee's beneficiaries shall serve all pleadings and all other litigation papers on the department and the uninsured employer, regardless of whether the department or the uninsured employer is a party to the particular action to which the papers relate.