KOO - You are correct as per the Bus. Corp. Act. Your first parafraph below is too general but the scenario you pose in the second paragraph is correct. The first paragraph should have said not less than 90% of the shares not already held by the offeror. That fits your second paragraph where the HL and EC shares would be held by the offeror so 90% of the remaining 45-50%.

"It is not 2/3. The offeror requires 90% approval of shareholders for a takeover." 

"So to take your example (as I understand it) should Eastern sell to HL, that would give HL approx 50-55%+. Then HL would need 90% approval from the remaining shareholders which may be difficult to get unless HL makes a valid buy out offer. "