Comment by NikkiA

There is a runway (YWKS) on antarctica 'moderately' close to the point where the midpoint of the great circle for that flight is, I'm willing to bet it's used as a diversion point for ETOPS purposes for those flights. It couldn't handle airliners daily, but in an emergency (in summer at least) I bet it could be mobilized just fine.

edit: allegedly YWKS does have a regular A319 service from Australia.