I gather that the Pod requires low voltage DC power from an existing VDSL cabinet . . .
Yes, that is the usual case.
. . . so I wonder what the increased battery drain might be during a power outage ?
I'm not sure if any figures have been published with regards to the extra loading as a result from the connection of the pod-based Nokia or Huawei equipment.
Is there any power protection facility such as a circuit breaker provided for the power cable between the VDSL Cabinet and the PCP Pod ?
I would imagine there is such a device at the "fibre" cabinet end. Within the pod, there certainly is a means of isolating the equipment from the incoming power supply.