Interesting scenario you have put forth. I would think that a few actions would take place if one of the suitors became very serious about making an offer.
I would believe the suitor would be slowly gobbling up shares of OK over a period of a few months so as not to cause a strong move up in the share price. I would think they would step in the market on an intermitent basis so as not to signal any intentions and obtain a better average price of acquisition over time. I would tend to think that a serious acquisitor would have stepped in during the trading day of the recent RE release and shortly thereafter as significant volume changed hands.
Also, the acquisitor at this stage would likely want to ensure that they stay slightly below the "insider reporting" threshold of 10% of issued and outstanding shares. Could you imagine what may happen to the share price if, for instance, Goldcorp announced it raised its' stake in OK to 10% or more. People/speculators would start piling into OK in a big way one would think !
Gary has made reference to 4 serious parties that have signed CA's. If I were a rep of one of these companies and liked what I saw, I would buy the stock and even in the event that my company was successful in a buyout, the return on investment upon takeover would likely more than offset costs of due diligence and then some.
Because of the insider reporting requirements, I would guess that we may see some less discrete buying by an acquisitor immediately before a public release of takeover as at that stage, they would be less concerned about tipping their hat and presumably would still be able to acquire stock below the agreed upon price. This is as you described it Milsy1 as the period just before the public announcement.