The organization of the moderators team is informal. There is no hierarchy and there are no assigned roles. Of course, a less experienced moderators might ask more experienced ones for advice at times. There is no separate reputation-system either; in principle, there is statistical data on our activity.
While this is not formalized, in practice there is a certain separation of tasks, which put itself in place naturally.
We have no system in place to assure complete coverage around the clock. If something catastrophic would happen, SE could step in.