It doesn't matter if they own 10% of the B shares. The board holds the real power. I know that Keevil said he wouldn't stand in the way if the majority of the B voted to accept the bid but he also said he would follow the board's recommendation which thus far is against it. The consensus opinion is that a copper spin off would be more valuable that the whole company as it now stands. 
I don't see how the board approves the sale if there is more money to had by a split.