I think the adv. train is made for house corporations only? So it doesn't really fit in with pirate RP, by the way pirates are not neutral. They're pretty hostile to house corporations, hence the pirating.
For example, to smugle cardamine to NY and slaves back, they are being smuglers and the smugler id says 4300 i guess.
If they are carrying food, water, Hfuel, etc, than yes they may use the adv train, but in my point of view, it doesnt suits them, if i see one of the adv train with an OC id i m thinking "powertrader", just the use of an id/tag to get safe on the OC side.