Bud - I think you are on the right track but would like to make two points.
I think PTX sells off one or two of the holding companies (drugs) and dividends cash to shareholders, and then only spins out to shareholders shares in the one holding company left, as opposed to spinning off all three to shareholders immediately. I think they have concrete offers on one or two drugs and that such offer(s) are the reason they are splitting the company in the first place.
Secondly - you simply can't say that if GSK, which is trading for $39, were to buy one of the holding companies that shares in that HC would be worth $39 each. GSK would value the HC at what they think it is worth, then pay that for the HC (could be in cash or in shares or a combination). The HC shares would then be worth (total purchase price)/(# of shares).
If I could afford to buy all of them, I would not need to buy any of them and I sure wouldn't be spending time on the message boards!