I've always taken "public ownership" to imply "publicly-traded company", which means John Q. Public can call up his broker and buy some shares in the company.
This in contrast to privately-held companies, which can and do have many owners, but whose owners are acquired through partnership, investment, key employees within the company, and M&A - but not through the sale of securities.
This in contrast to privately-held companies, which can and do have many owners, but whose owners are acquired through partnership, investment, key employees within the company, and M&A - but not through the sale of securities.