Section 21. Subject to approval by the secretary of health and human services, the commissioner may enter into interagency agreements with the commissioner of developmental services for the coordinated regulation of or for the coordinated or joint management of certain services that are required or that must be provided by both the department of developmental services and the department of mental health. Such agreements may be entered where it is determined by the commissioners of said departments that the services require coordinated regulation to ensure development of substantially similar standards consistent with certain shared needs of mentally ill and persons with an intellectual disability or that the services will be more efficiently and effectively provided by a single, unified management system than by two separate management systems. Such services may include, without limitation, transportation, laundry, data processing, certain services to mixed populations of mentally ill and mentally retarded individuals with common needs for care and treatment or to individuals who are diagnosed as both persons with an intellectual disability and mentally ill, research activities and program monitoring. Coordinated regulation of such services may include, without limitation, such issues as restraint, charges for care, investigations and case management. Pursuant to such agreements the department of mental health may assume responsibility for the provision of such services to the department of developmental services. Such agreements may delegate responsibility to the department of developmental services to provide such services for the department of mental health. Such agreements may provide for the expenditure of appropriated funds consistent with such joint management service systems and may further provide for assignment of certain staff to such joint management service systems. Such agreements shall not, however, conflict with the department of developmental services' primary responsibility for persons with an intellectual disability regardless of whether such persons are also mentally ill.