750 ILCS 90/60

(a) A privilege under Section 55 may be waived in a record or orally during a proceeding if it is expressly waived by all parties and, in the case of the privilege of a nonparty participant, it is also expressly waived by the nonparty participant. (b) A person that makes a disclosure or representation about a collaborative process communication which prejudices another person in a proceeding may not assert a privilege under Section 55, but this preclusion applies only to the extent necessary for the person prejudiced to respond to the disclosure or representation.