When a president, bishop, or high priests group leader is released, the counselors or assistants are released automatically. Others who hold positions in the organization, such as clerks, secretaries, and teachers, are not released automatically.
Based on this, I would assume that if a bishop (who is the Priests Quorum President) is released, then the Priest Quorum Assistants are also automatically released.
In LCR, if you release an auxiliary president, the counselors are released automatically. However, if a bishop is released, the Priest Quorum Assistants are not automatically released. Is there a reason for that? I can't find anything in the Handbook, that would say that they are an exception to the rule.
(I can't remember if the counselors in the bishopric were automatically released either. I do remember that even though it is the stake clerk who records the releasing of the old bishop and the calling of the new, it is the ward clerk who records the new counselors.)