With respect to any minor for whom the Department of Children and Family Services Guardianship Administrator is appointed the temporary custodian or guardian, the Guardianship Administrator may designate in writing a private agency or an employee of a private agency to appear at court proceedings and testify as to the factual matters contained in the casework files and recommendations involving the minor. The private agency or the employee of a private agency must have personal and thorough knowledge of the facts of the case in which the appointment is made. The designated private agency or employee shall appear at the proceedings. If the Court finds that it is in the best interests of the minor that an employee or employees of the Department appear in addition to the private agency or employee of a private agency, the Court shall set forth the reasons in writing for their required appearance.