Ex...
In short, no.
In long, yes, but not "on the fly" - it would take technicians to modify settings in the voice switch hardware/software. If the CH Centre is wiped from the face of the earth (including the contingency centre in the adjacent building), then we invoke emergency procedures (basically TIBA) and each tower "attempts" to retrieve local flights. Obviously this relies on pilots a) recognising that the centre is no longer transmitting (hopefully a warning broadcast would be made by the centre before going off air, but no guarantee) and b) knowing what frequency to select to receive the EMG service. It's all described in the AIP EMG sections...but how many are familiar with these without referring to them. I'd guess a few more are following the weekend's events!
There is another "contingency centre" setup in a portacom behind the TWR/OCA building, but no one local in Auckland (with relevent current validations) to staff it.