The provisions of this article shall be operative in any county in which the board of supervisors by ordinance finds, on the basis of employment conditions, the state of juvenile detention facilities, and other pertinent circumstances, that the operation of this article in that county is feasible. In such ordinance the board shall prescribe whether the probation officer or any official in charge of a county juvenile detention facility shall perform the functions of the juvenile work furlough administrator. The board of supervisors may also terminate the operativeness of this article in the county if it finds by ordinance that, because of changed circumstances, the operation of this article in that county is no longer feasible.