"They own NOTHING. They are buying NOTHING, except the contract from a British company to load and unload cargo."
That's not true!
They are buying the net asset of the company and the present value of its future earnings. They are moreover buying goodwill, and a host of other intangible assets such as trademarks and patents.
Will the terminals still have a P&O logo?
NO!
Are you claiming that P&O has the trademark and/or a patent on port terminals that they use?
If so, then you are utterly and completely wrong!