We wouldn't pay for travel from overseas back to Australia I wouldn't think unless there was a major disaster, such as the Tsunami or Bali Bombings for instance. However since they were still Australian citizens they would have been covered by medicare as long as they were on home soil while their medicare card was still renewed. But not indefinitely.
I once lost access to medicare in Australia because I let my renewal slip, and since I hadn't needed it for more than 5 years it became inactive. I then could not get back on medicare until I proved to them I hadn't lived abroad, or was back here for good. Since I hadn't lived abroad and moved back this was impossible to do. And no my passport showing no overseas trips was not enough.
They decided I was lying about my lack of need for medical attention and made me jump through every conceivable hoop to get back on it. I got back on it eventually, but I had to go back to square one and prove my existence, prove that I live here, that I work here, that I was BORN here!! And that I had BEEN here consistently for the last 5 years. Crazy.
You know also if AB forged 'biomums' signature on the passport application, it would not be such an unusual thing for someone to do in Australia, I have come close myself many times when dealing with government departments here ... for my own sanity I choose 'not to engage' for the most part.