The loan agreement lists the terms under which a loan is given. The bank is the lender, and any borrowing entity--individual, partnership, company--is the borrower. The loan agreement covers many of the same terms and conditions as a promissory note, although it is longer and more complicated.
The subsidiaries remain private. They are private subsidiaries of a public company. Think about it: if a subsidiary went public, that would mean that its shares were being offered to the public, instead of all being owned by the parent company, and so it would no longer be a subsidiary.
The individuals then become shareholders in the holding (parent) company, and the parent company owns the shares in each of the original companies, which then are subsidiaries of the parent.   Indiviuals own shares in parent. > Parent owns shares in each subsidiary.