Was the second part of your question on what document would cover the MRB?
It is probably controlled by your quality manual, or BMS process flow.
One area that is missing from my current employer is the MRB's obligation to document and retrain operators on acceptable criteria.
We can deem the same defect as acceptable every day for a month, without communicating to the person tagging the part what truly makes the part conforming or nonconforming. Because of this, the MRB team, which has significantly higher salaries, takes time to disposition a part, when the call could easily be made by the operator.
Another benefit to MRB is, when a part is "iffy" and we want to ship, no single manager will be held responsible if the part is rejected by the customer. If one person had to make the call, they'd probably always play it completely safe.