(a) Unless otherwise provided in a plan of merger or share exchange or in the laws under which a foreign business corporation or a domestic or foreign eligible entity that is a party to a merger or a share exchange is organized or by which it is governed, after the plan has been adopted and approved as required by this chapter, and at any time before the merger or share exchange has become effective, it may be abandoned by a domestic business corporation that is a party thereto without action by its shareholders in accordance with any procedures set forth in the plan of merger or share exchange or, if no such procedures are set forth in the plan, in the manner determined by the board of directors, subject to any contractual rights of other parties to the merger or share exchange.