Personally i don't see Arena getting paid at all and if they do it won't be for the full amount. They have shown just how greedy they are and thought NXE would just lay down and take it.....but now you are triggering unconscionable conduct clauses which are built into most contracts these days with regard to that termination fee and with the governing law being in Western Australia they have really outsmarted themselves.They are not going to want a long drawn out court case which can become expensive not only from a cost point of view but also time.
If you then add to the fact that NXE have a very substantial claim against them then you would say that NXE are very much in the drivers seat and could actually come out ahead if they play their cards right.