Geez That guess was something of a what we call here at Railpage a WSITD (wild stab in the dark). Had no idea that the dart would land smack in the bullseye.
The suggestion of an embankment made me think of how the Eugowra branch at its beginning snakes all through Cowra on a series of embankments and (now removed ) trestle bridges.
I'm working very early in the morning, and so have to hit the cot now.
Be patient good peoples and I'll find something to post tomorrow arvy
And there I was thinking that you must have some inside info!
But, you are clearly as good a detective as Inspector Morse ever was when it comes to evidence of old railways.
Btw, if you have never seen the episode in question, it is worth a watch, not only for the railway interest but also for the surfeit of archetypal "Australianisms" (as judged from the UK, presumably, but maybe with advice from ABC or whoever) incorporated in the plot and script. For example - all watching the Melbourne Cup in the pub; pommy bastards; she'll be right, mate (parting words from the NSW detective to Morse). Makes me feel right at home!