I don't understand options stategies too well. However whatever way it works, if Ackman has hedged his short with options, somebody else must be at the other side of that trade? If ackman is buying puts (the option to sell the stock) then the other side is selling the option to sell. Does that mean that the other side of ackman's trade (if they did not already own the stock) will now be short? Sorry for the convoluted way of explaining my question?
Could be, or they could just carry a naked position. For example, I have sold some of my stock and sold puts to replace them. Looks like Ackman was buying from me on both legs :-) More seriously, from the description of his position sizes, it looks like he has bought Jan 15 puts.