Complex sentence: The laker fleet, the B&LE, and the DM&IR all belong to Canadian National after U.S. Steel sold most of Transtar to that company, although the ships are leased out to a different, domestic operator because of American cabotage law.
Split into simpler sentences: The laker fleet, the B&LE, and the DM&IR were acquired by Canadian National after U.S. Steel sold most of Transtar to that company. The ships are leased out to a different, domestic operator because of United States cabotage law.