The lender or the acquirer would only get control if the borrower was in arrears on their loans.
In the case of the Quinn Group, a receiver was appointed to the shares in the group, because the shares had been given as security for loans.
In most other cases, the company gives property as security for loans and the lender can appoint a receiver to sell the property.
In some cases - Arnotts may be an example - the loans are written down and the lenders are given shares in the company instead, thus effectively taking control.