If I remember correctly there was an article posted in another thread that they were buying the stock as when the new stock comes out. It will be sold to people/companies based on percentages of the old stock they owned.
IE: MS owns 25% of the current stock and that is the biggest share then they will be able to buy the biggest share of stock when it comes out @ the IPO price. From the article I think it was like 25% old stock may equal 15% of the new stock.
They were also getting millions of shares as they are the broker and if not all bought they have to buy them.