Sorry, little beind the times on the info, what did happen to the Australian prints? Were they video or film?
Overseas broadcasts prior to the mid-70s were 16mm film. From season 10/11 onwards broadcasters started to request 2" quad tapes.
Power:
Australia - Returned to BBC London in 1975
New Zealand - Sent to Singapore in 1972 (IE there were only two sets of prints sent round the world over three countries)
Evil:
Australia - Returned to BBC London in 1975
New Zealand - Junked by the NZBC prior to 1974
If you want some bedtime reading, you can look here:
http://missingepisodes.blogspot.co.nz/p/howmanyprints.html
Though parts of the bicycle chain is out of date in light of new information, and I hope to update it in the coming months.