Mont. Code Ann. § 19-1-402

19-1-402 . Contents of federal-state agreement. The agreement authorized by 19-1-401 may contain provisions relating to coverage, benefits, effective date, and modification of the agreement, administration, and other appropriate provisions as the department director and the commissioner of social security agree upon. Except as otherwise required or permitted by the Social Security Act regarding the services to be covered, the agreement must provide that:

(1) benefits will be provided for employees whose services are covered by the agreement and for their dependents and survivors on the same basis as though the services constituted employment within the meaning of Title II of the Social Security Act;

(2) the agreement must be effective with respect to services in employment covered by the agreement performed after a date specified in the agreement, but may not be effective with respect to services performed prior to the first day of the calendar year in which the agreement is entered into or in which the modification of the agreement making it applicable to services is entered into, except that the effective date may be made retroactive to the extent permitted by section 218(e) of the Social Security Act, 42 U.S.C. 418(e);

(3) all services that constitute employment and are performed by employees of the state must be covered by the agreement; and

(4) all services that constitute employment, are performed by employees of a political subdivision of the state, and are covered by a plan that is in conformity with the terms of the agreement and that has been approved by the department under Title 19, chapter 1, part 5, must be covered by the agreement.