I agree, that although I can't pinpoint the actual location of where the video from the XPT cab was taken, as a regular traveller on the Hume Freeway which is clearly shown on the left, this is one of the few locations between Barnawartha and Bowser where the Freeway parallels the rail line. As there are only two tracks shown, with the converted broad gauge on the right, it's way north of Seymour (and Wallan) where the broad gauge to Shepparton diverges from the North East Line corridor.
Just finished watching the video which appears to have been taken from an XPT cab and does cover the Wallan area. The track is shocking.
The reason people are referring to the track conditions post this event is simply because the track (main) was out of service by accounts and that was due to the condition of the track.
I don't think this is accurate, the video I saw was in NE Vic at Bowser, which is approx 200km away from Wallan.
Also, from reports the main was not out of service at all, trains had been traversing the section the days leading up to and including the day of the derailment.
I also agree with other posts that an unfortunate confluence of events led up to this accident and the track condition in itself wasn't a direct cause as some would like to make out. However, that doesn't excuse the low priority given to maintaining the track to an acceptable standard allowing passenger trains, few as they might be, to operate at their maximum speeds without undue discomfort, which is obvious from the video at only 80km/h.
What hasn't been mentioned so far, is that the SG track between Melbourne and Albury forms part if the Inland Rail Route between Melbourne and Brisbane. You would think that it would warrant upgrading to comply with what will hopefully be a higher standard for the Inland Rail infrastructure, allowing higher speeds for heavier freight trains.
From my reading on this and other blogs, it seems that the SG line from Albury to Melbourne was constructed on the cheap and it has been a problem from the very start. All the ARTC and its contractors have been doing is trying to patch up past mistakes. Perhaps the only solution to fix it, is to pull it up and start again.