The merger ratio is indeed 2:3 i.e. 67 shares of ICICI Bank for every 100 shares of I-Sec.
ISEC_29062023144353_Outcomeofboardmeeting.pdf (nseindia.com)
The bank is side-stepping the reverse book building process by doing the delisting under a special provision where the holding company and the subsidiary company are “in the same line of business”. But are ICICI Bank & I-Sec in the same line of business? Not sure how this is interpreted legally, and whether there is any such precedent.
It seems the delisting will require approval of twice the number of non-promoter shareholders than those opposing it. So if more than 1/3rd of minority shareholders oppose it, the delisting will not go through. See page 24 of the attached document.
(Disc: No positions)