(b) Each probation agency or department is authorized to enter into a contract with the appropriate local social services district for the performance of the functions of the support collection unit, in accordance with the provisions of section one hundred eleven-h of the social services law. 7. The provisions of this section shall not apply to any county that is located wholly within a city; provided, however, that the provisions of subdivision six of this section shall apply in like manner to any county that is located wholly within a city.