How? And which ones? Does this still apply when the restricted areas are active?
Saying you can land there in an emergency and nominating it as a alternate are two different things.
A mate who is an International 747 captain told me his airline uses woomera as a waypoint / alternate. It allows them to reset the fuel reserves enroute to Melb.
Woomera became dramatically more difficult to access when Airforce took it over from the Dept of Defence about 3 years ago, but it used to be relatively straight forward. It would certainly be very do-able with 30 min notice. In that era the restricted areas where not active very often. Even now they are frequently inactive. If there was a compelling need to land there I have no doubt it could be arranged at short notice. The ARO's there are very sharp. There is one on duty 24 hrs per day 365 days a year.