US government has shown interest in Canada's method of monitoring and benchmark port productivity.
Port's volume fell nearly 10 percent in 2015.
Central Japanese port kept title for fifth straight year despite a decline in overseas shipments.
The union and APM Terminals agreed to return to the negotiating table to settle year-long strife.
The legal salvo is the latest sign of how Hanjin containers continue to disrupt the global container shipping market.