Tony said yesterday there are 3 major companies - UAE, Hong Kong, and Singapore.
Like all global industries, the port operations industry has been consolidating over the years. The US dropped out of the shipping industry in the 70's because, as LibertyLee points out, there's not very much money in it. You'll notice the countries that have big port operations industries are small nations that want a global economic footprint.
The only other company that conceivably could absorb P&O, the British company, is the Singaporean company.
Thanks for the info! FWIW, with that as my choice, the UAE might very well be the pick of the chicks.