There is no definition of unacceptable circumstances. The Panel's ability to make a declaration of unacceptable circumstances is broad. Guidance Note 1 provides an overview of the Panel's apprGuidance Note 1oach to making a declaration of unacceptable circumstances, including the Panel's powers and the circumstances in which the Panel may declare circumstances unacceptable. See for further information.
The Panel has the power to make orders to protect the rights of persons or groups (especially target company shareholders) during a takeover bid and to ensure that a takeover bid proceeds (as far as possible) in a way that it would have proceeded if the unacceptable circumstances had not occurred.
The question is how can they allow delisting to occur yet protect other shareholders interests?
https://www.takeovers.gov.au/content/DisplayDoc.aspx?doc=about/about_the_panel.html