New preliminary report out today.
https://www.aibn.no/Aviation/Investigations/16-286
"The observed failure mode in this accident, i.e. crack initiation and propagation with limited spalling, seems to differ from what was expected or foreseen during the design and certification of the main rotor gearbox. The fracture propagated in a manner which was unlikely to be detected by the maintenance procedures and the monitoring systems fitted to LN-OJF at the time of the accident."