I have no knowledge; I suppose some are, some are not - yet, that's not illegal and not what Hollywood accounting is all about.
Apple, Microsoft, Google, Ikea and anyone else who can are all doing the same (google "Double Irish Sandwhich" for an example). I think it should be illegal, but apparently it isn't, and if Apple can do it, Hollywood can too.
Hollywood accounting is all about making sure that there is no direct profit booked, so that profit sharing (which they manage to sell even to people who should know better like Stan Lee) essentially become free labor/assets.
And then go after the amount lost in tax revenue.