The line stopped seeing regular use once the Boort goods ceased running. All grain from North of Inglewood goes via Maryborough, and all local grain goes via road.
After the Boort goods ceased, floods washed away large sections of the line (a few years back now). Without the regular traffic it once had there was no reason to repair the flood damage. This has not changed.
Without significant corporate interest, there is little likelyhood of this line reopening. If this line was to be reopened in the future, it would need significant work, similar to what has been done to the Ararat - Maryborough line.
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As for SG into Bendigo via Inglewood, the main issue is the route you are building. What's the point? If your aim is to send freight to Melbourne, then use the BG, its already there. If you where to put in SG to Bendigo via Inglewood, then it will certainly be travelling the long way to get to Melbourne via Dunolly, Maryborough and Geelong.
If your aim is to send freight from Bendigo to interstate markets, then that is even worse. Bendigo to Seymour is 1 hr 15 min by road. If you were to build an SG link from Bendigo via Inglewood, Dunolly, Maryborough, Geelong and Melbourne that is going to take what? 10 hours? More? You just aren't going to be competitive.
The only advantage I can see is if the destination for your freight is either North of Inglwood or Dunolly, The Port at Portland or anywhere West of Ararat. I'm no expert, but I doubt there is enough demand for that particular freight task to justify the cost of re-building and converting this line.
I am all for building new rail infrastructure, but there is so much we need that will not be built soon enough, or that will just never be built at all, we shouldn't worry about the stuff that doesn't come anywhere near stacking up.
At the end of the day, if their is enough corporate will for it, it will be built.