(a) In any case in which a prisoner was sentenced to the state prison pursuant to Section 1170, or if he committed a felony before July 1, 1977, and he would have been sentenced under Section 1170 if the felony had been committed after July 1, 1977, the Department of Corrections shall have the authority to reduce the term prescribed under such section by one-third for good behavior and participation consistent with subdivision (d) of Section 1170.2. A document shall be signed by a prison official and given to the prisoner, at the time of compliance with Section 2930, outlining the conditions which the prisoner shall meet to receive the credit. The conditions specified in such document may be modified upon any of the following:

1. (1) Mutual consent of the prisoner and the Department of Corrections.
2. (2) The transfer of the prisoner from one institution to another.
3. (3) The department’s determination of the prisoner’s lack of adaptability or success in a specific program or assignment. In such case the prisoner shall be entitled to a hearing regarding the department’s decision.
4. (4) A change in custodial status.