Re: They already have a legal route
The Irish authorities are not looking the other way, they filed a brief with the US courts reminding them that Ireland is a sovereign nation with all that implies. So far, nothing has happened which is actually in breach of European and Irish data-protection law (at least officially). The EU is on record as pointing out that while they are monitoring the case, it is a matter for Ireland and the US in the first instance.
To say MS Ireland are safe is complete nonsense. MS Ireland are unarguably the Data Owner within the framework of the Irish Data Protection act. By allowing MS US access to that data without explicit authorisation, MS Ireland are unquestionably in breach of the act. While they may not be able to prosecute the US employees, they can prosecute the subsidiary.
This really is a case of "goodnight US cloud in Europe" if MS lose.