The following is the view from the Block 5 rep on this topic: from his letter
Administrative Grievance 10-02 (Pilot In Command on Augmented Crews): Settlement Agreement
Wrapped together with the TA’d CBA sections, the MOUs, and the LOAs are two grievance settlements. The first, Administrative Grievance 10-02, deals with the designation of PIC when two captains happen to be crewed together, and for some reason, the Captain captain with the highest system seniority is not the pilot in command. Although the affected pilots suffered no economic harm, they will receive an economic reward in the form of hours credited to their compensatory makeup banks, which allows them to pick a trip and receive compensation at 150 percent of the normal pay rate. The method agreed to for determining PIC is essentially the same as that which is published in the latest version of our Flight Operations Manual (FOM).