A friend told me about a 2018 book " Blue Lake,. Finding Dudley Flats and the West Melbourne Swamp", by David Sornig
It's a factual narrative about the 8km square zone that housed tips, bone-yards, marsh-lands derelict railway lines, and the people who lived in humpies of scavenged materials through the depression into as late as 1957.
It closely examines the lives of people who lived there, in one case for over 40 years, and another who lived in the carcass of a beached vessel, a lighter.
It's a really good read. There were several copies in our local libraries.
On page 311, there is a mention of the continued use of the area by trotting trainers:
In June 1950, a conference was held between the Melbourne City Council, Victorian Railways, Lands Department and Trotting Control Board (which had a stake in the area as the operator of a nearby trotting track ) to try and stem the illegal dumping of rubbish along Footscray Road.
People were still living around these tips and scavenging materials from them.
The -re-development of the area into a container shipping and transport hub didn't commence until 1958.