I think "hushed up" is journalistic licence. I've certainly read about this disaster in railway books.
As a poster on the Google uk.railway group says:
I don't know how hushed-up it was. It's in several books on railway
accidents, including Peter Semmens' "Railway Disasters of the World".
I'm also pretty sure it's in P.M. Kalla Bishops book describing his
work in Italy with the British military when he was in charge of the
Italian railways at the end of WW2.
