" ... to implement a single application process and single examination process for New Zealand and Australian patent applications.Further details are available here.
The single trans-Tasman application and examination processes for patents, along with the passing of the Patents Bill, are part of the Government’s Business Growth Agenda initiatives to encourage and support innovative industries".
The Single Patent Examination Factsheet, here, and the information available from Australia, here, give no clue regarding challenges to a patent's validity, rather giving the impression that each jurisdiction will continue its own revocation proceedings. PatLit thinks that there may be some interesting issues arising in terms of, for example, the precedental value of the decision of the first court to rule on a jointly-examined and granted patent the validity of which is separately challenged in the two jurisdictions.
Thanks go to Chris Torrero for spotting this item.