Jadran you're more or less right, but that's because the Jones-act US-flagged vessels from Sea-Land were all with a steam turbine, so all those went to CSX. The ones on international trades, non Jones-act, were taken over by Maersk.
Now later on CSX, or actually Horizon, had some motor-ship (Hyundai Mipo built) charter container ships on non Jones Act trades.
Regarding the charters at the time of take-over, most of them were ended soon but Maersk took over some charters, for various amount of time.
Cheers,
Roy