I can think of one possibility you might be able to investigate. In order for such a procedure to be used, there would have to be a "power of attorney" or some similar legal instrument giving the "stand-in" the authority to act for the absent party. The power of attorney would have to be recognized as authentic and binding both by the absent party (in this case, in Australia) and by the local authorities in Switzerland.
Oddly, I have an example of this procedure from a century earlier (1825), when one of my ancestors, then living in Kentucky, USA, inherited a modest sum from a relative in Lausanne, Switzerland. The discovery of this situation was a rather startling accident: An extremely distant cousin, Catherine, (12th cousins, from a 16th Century pastor in French-speaking Switzerland) lives near Paris, but frequently travels to Switzerland for research in various archives. She happened to come in contact with a woman living in Alsace, Irene, who descends from one of my Swiss ancestors, from the Marcel family. They had grown up in the same part of Alsace, and so arranged to meet. Irene descendant brought out a few family documents, including one that she didn't understand. Catherine glanced at the signatures and just about fell off her chair: there she found the clear signature of a David McCoy! What was this document, and how did it end up in Alsace?
In order for the relatives in Kentucky to receive the Swiss inheritance, the family in Kentucky went before the county court to register a power of attorney. The court attested to the identity of the family members who signed the document, and sent the document to the chief justice of the state court, who attested to the signature of the county judge and forwarded the document to the next link in the chain. At each step the signature of the preceding link was verified, until the document reached the US Secretary of State. The next link was a US Chargé d'Affaires in Paris, who passed it on to the Swiss Ambassador, then down the line through several successive steps until it reached the appropriate court in Lausanne. When the whole process was settled, the original document ended up in the hands of the representative of the family in Switzerland, who later migrated briefly to the US and then to Alsace, and the document was passed down through several more generations there.
The method of conveying the authorization for someone in Switzerland to act in the interest of someone in another country is what we mean by "diplomatic channels". There should certainly be records of this sort of transaction in both countries, if we knew where to look and had access. For Switzerland, there should be registers of diplomatic correspondence in the federal archives, but we were not able to find them. For the US, I was able to learn that there is a long series of volumes of copies of correspondence from the Department of State that appear never to have been indexed. It would take a lot of research in the US National Archives, and I have never had the opportunity to do so. There may be other routes that a power of attorney could take, perhaps from a local court through a Swiss embassy or consulate. In any case, I expect there must be a huge number of stray "diplomatic" records around the world relating to inheritance, property, and other matters for families with members living in different countries. I hope more of these will turn up as new generations of archivists digitize everything!