From the SMH:
http://www.smh.com.au/nsw/train-derails-at-edgecliff-20140115-30v0t.html
Train derails at Edgecliff January 15, 2014 - 6:06PM Date A train has derailed between Kings Cross and Edgecliff, causing the partial closure of the Eastern Suburbs line. Pictures from a train passenger show a large piece of metal piercing the floor of the train carriage.
That is rather unbelievable. Wonder that that bit of metal is. There's not exactly much of it in the tunnels on the ESR line.