RE: potential buyersThat seems to be the logical thing to do STE15165, but in many cases companies do not own stock or very little when they make a purchase. I guess it depends on management's style. Take the case of Hudbay buying Norsemount for the Constancia project. Hudbay had about 1.3% of shares in Norsemount when they made the offer and they had plenty of time to buy shares as they had been in talks for 1.5 years before making the move (started talk in mid 09 - deal made Jan 11).
Also keep in mind that a company would have to disclose once they own 10%. So let's say for the exercise that they managed to save $1.5 on 10% or even 15% that may come out to a savings of $20 to $30M on a $600M deal. But, in doing so, the major would be tipping their hands to their competition which they usually don't like to do. (these #s are crude but it gives an idea)
On the other hand you have some that are completely open about it. As I said, it depends on management and their strategies. We haven't seen any major buying or accumulation as far as we can see, but who knows for sure.
jmho
P-Air