<<If Woodside was mislead by PXD into this whole deal and was assured by PXD this was no illegal farmout and everything was legit, couldnt Woodside possibly have a case against PXD>>
Yes, Woodside could bring an action against PXD if that is the case, imo.
<<Or does the fact that Woodside hasnt filed against PXD possibly mean that they share knowledge and responsibilty for this illegal farmout>>
It's hard to say without having first hand, inside knowledge of what both parties knew, when they knew it etc. Perhaps Woodside is showing unity with PXD because they never thought the case would make it this far so there was no reason to immediately attack PXD. I have no doubt that if Woodside does see this as being possibly a very harmful outcome for them, they will do what's best for them and leave PXD behind, imo. If Woodside is harmed from this lawsuit and they truly were unaware about the illegal farmout, i would think they would sue the pants off of PXD.
<<Obviously MOSH Holdings has reason to feel Woodside is a guilty contributor to this illegal farmout or they wouldnt have included them in the lawsuit>>
I am sure MOSH has evidence which shows who knew what, when they knew it, what each of them did with regard to the farmout etc. However, even if it's not as black and white, MOSH had to bring in Woodside because it wouldn't be prudent for them to presume Woodside is innocent and just sue PXD. If Woodside is really innocent, then Woodside can try to prove it to the jury but that is not for MOSH to determine beforehand.