"Code sharing" was just a way for me to use some shorthand in a way that most people would understand. Ocean Carriers are very similiar to Air Carriers. They have high capital costs (vessels and planes). Their service is usually built around a port rotation. And their provisioning is restricted by slots/seats.
The difference in service comes into play when the cargo hits the ground.. so the ocean lines (in an effort to not commit suicide via price wars) got together and decided to split the cost of the commodity (the carrying of a container over water).
So you can have cargo travelling under a P&O Neddlloyd Bill of Lading, inside a NYK container, laden on an OOCL vessel being serviced by a port run by K-Line.
Which is directly related to this issue.. because no matter who the players are.. US CUSTOMS IS US CUSTOMS. US CUSTOMS (FDA, USDA) are the gatekeeper.
"So you can have cargo travelling under a P&O Neddlloyd Bill of Lading, inside a NYK container, laden on an OOCL vessel being serviced by a port run by K-Line."
Very good summary.
It's also worth noting that these "alliance" relationships are one of the key reasons why so few maritime shipping conglomerates are U.S. companies. Most of them operate in these cartels like the one you just described, and this kind of relationship between these companies would likely be a violation of U.S. anti-trust law.