People use the pirate train for lawful trading and its kinda cheap, they just do it because it is the next biggest ship. You can dock with lawful bases, and most of my smuggling routes are not 100% contraband. They usually range from 50% to 75% contraband. So trading legal goods is okay, as long as you have a smuggler ID, and you smuggle as well as trade.
To be honest i forgot reading the infocard cause it was sold on a freeport.
I use the pirate train for legal trade in or via the borderworlds where a ship built by the known companies would draw more suspicion from pirates (IMG id and tag)
(i had many traders but this is the ship with the right balance between agility ,cargo hold and armour also the defensive capabilitys are better than a advanced train and this one rarely gets stuck in a trade lane or jump hole)
since i am no pirate or smuggler and dont want to fly a ship wich makes me an oorp trader, i already swapped back to a Heavy tanker wich seems to be the closest match to the pirate train.