Cal. Welf. & Inst. Code § 11324.5

The county shall ensure that the labor union is notified of the use of participants assigned to an employment or training program position described in Section 11322.6 or 11322.9 or any positions created under any county pilot project, in any location or work activity controlled by an employer and covered by a collective bargaining agreement between the employer and a union. For nonunionized employees, procedures shall provide for notification to employees of the use of participants under this article and the availability of the grievance process. Display of a poster shall satisfy this requirement.