Norwegian article with several statements from Halvorsen from ABIN:
Havarikommisjonen: Dette forårsaket helikopterulykken - Bergens Tidende
He says the gear box had been in a road accident in Australia, and gotten damaged, and then sent to Airbus, who checked it and approved it for use.
Also he says that there was nothing that could have been done, maintenance wise, to discover this fatigue crack.
"- Det betyr at vi mener dette var en feil som var umulig å detektere med vanlige vedlikeholdsrutiner, sier Halvorsen."
Translation: "This means that we are of the opinion that this was a fault that was impossible to detect using ordinary maintenance routines, says Halvorsen"