Its interesting alright. I would never rule out a P&O Ferries - Irish Ferries merger. I don't know what the competition authorities would do, probably block it. However it would give both operators access to routes in both in the North and South, and through 'landbridge' Irish Ferries would have access to P&O North Sea, and P&O Short Sea. Additionally P&O would have access to Irish Ferries Ireland to France operations. - It would be an interesting alliance, certainly strengthen both companies. As in the airline industry you have Skyteam, and Oneworld. Could this model be employed in the ferry sector?
P&O however are doing very nicely on the central corridor, as are Irish Ferries. P&O's crewing costs aren't as much as the competition, the ships are very fuel efficient, and operate to capacity. The only negative is the longer journey time = more fuel burn. Still the route has become very popular with hauliers, and the general public. P&O's reliability is also pretty impressive.