During the times that grants-in-aid are provided or made available by the United States government for the purpose of defraying any portion of the costs of administration incurred for public assistance, the State Treasurer shall pay to each county an amount equal to the county’s proportionate share of the sum so granted for the cost of administration, which amount shall be used exclusively for paying the administrative costs. Except as provided in Section 15151.5, the department shall determine the portion of the amount so granted or made available for administrative costs to be paid to the counties, which portion shall be determined pursuant to rules and regulations of the department and shall be not less than one-half of the amount so granted or made available. The
department shall adopt rules and regulations that shall be of uniform application for determining the proportionate shares of the respective counties of the portion so determined to be paid to those counties.
This section shall become operative and shall supersede provision (2) of Section 15150 during the times that grants by the United States government, provided or made available to defray any portion of administrative costs incurred for public assistance, are not computed as a proportion of those costs of administration. Whenever this section is in effect, all other sections referring to Section 15150 shall also be deemed to refer to this section.