A prisoner whose release from the custody of the Department of Corrections is imminent and who may have a mental illness and be in need of hospitalization or treatment may be the subject of an involuntary admission proceeding under §§ 37.2-814 through 37.2-819 within 15 days prior to his anticipated release date, and any order entered in such proceedings shall be effective upon the release of the prisoner from the Department of Corrections. If a commitment hearing for involuntary admission under §§ 37.2-814 through 37.2-819 is combined for hearing or is heard on the same day with either a commitment hearing under § 53.1-40.2 or a proceeding under § 53.1-40.1, or both, only one fee shall be allowed for the special justice or district court substitute judge conducting these proceedings and only one fee shall be allowed for the attorney representing the prisoner in these proceedings.