I would agree Racedo with the "nobody held accountable for it". However I look at it from a slightly different angle.
The Mgmt team under Dermot Mannion came up with the 'leave and return scheme'......at some point someone in mgmt must have raised the question of possible tax implications. We will never know. Nonetheless the Mgmt team (with the blessing of the then CEO) gave assurances to the staff (who had tax concerns themselves) the this scheme was all above board and would result in no tax penalties for the individual staffers. In this way they got the staff to sign up for it. Someone then got a pat on the back and a bonus for the successful scheme to reduce annual salary costs.
The scheme backfired on EI mgmt and they were in a position of having to pay the penalty or returning to the original salary scales. So yes, someone/some people are responsible for the payout of that 30M. However I fear that the masterminds behind already had their bonus and had left before the Revenue caught up with EI. As I already stated the current Chief Commercial Officer of EI is the only senior mgmt figure who was involved in that....he seems to have escaped any culpability.
I do see your point on money being paid out. If the staff had blindly signed up to it and then claimed fault I would fully agree with you. However the staff did query the tax situation and where given assurances from EI that it was not an issue. SO my finger points at the mgmt team who gave those assurances in order to make their plan success without any long term thinking or future concern for the airline.