The FISC in France had a go at both RY and U2 a few years ago and it was all more or less over and done with within a couple of months and they were brought into the tax net - both staff and companies. How deeply into it, I'm not sure, but deep enough to the FISC's satisfaction.
Deep enough for Ryanair to close their French bases. The MRS 'summer base' is the only remaining and still of interest to the police. Or so it was a few summers ago anyway, I don't have the inner gossip anymore.