At the request of the Director General of the regional health agency for the zone, back-up interventions are initiated and coordinated by the emergency medical assistance service (SAMU) for the zone mentioned in article R. 3131-7, in the following cases :
1° When the network mentioned in article R. 6123-26 is unable to meet the emergency care needs of the population;
2° As part of an event mentioned in article L. 1435-2.