* Investa board to consider alternative Canadian bid, adjourn vote. : SYDNEY (Reuters) - Australian office landlord Investa Office Fund (IOF.AX) said it will study a $2.4 billion takeover bid from Canada’s Oxford Properties Group, an offer that was criticized by rival suitor Blackstone (BX.N) which also threatened to drop its own bid. Oxford had lobbed a last-minute A$3.3 billion ($2.4 billion) offer for Investa on Tuesday that was A$90 million higher than U.S. private equity firm Blackstone Group’s bid which had already won the backing of the target.