biz-buz,
You may wish to check the wording of the 'Austrian Control' decision. It might be it is because the AS355 is 'not compliant' with the extant regulations (what ever they are) rather than 'not safe'.
Safety in the context in the 'decision' might also have been taken against a 'safety case' - i.e. it does not meet the criteria which has been set by the regulator.
In my view EASA would be most reluctant to interfere in a case where they do not have legal competence.
As a matter of accuracy, EU-OPS has been the the EU regulation for a number of years now; however, helicopters are not included within its scope.
Jim