Notwithstanding the provisions of sections 15.51 to 15.57, a receiving agency in this state participating in an interchange of employees under the Intergovernmental Personnel Act of 1970 may enter into a written agreement with a federal agency. Such agreement may provide for the state agency to pay all or a portion of the salary and fringe benefits of the federal employee assigned. Such payments may be made directly to the employee or as reimbursement to the federal agency.