At least in the Northeast Amtrak heavily competes with the airlines. Most business won't pay for premium travel, so when it comes down to regional coach or delta shuttle, they pick delta shuttle. However, if there was a chance they would get upgraded to biz or on the Acela to 1st then they might go with Amtrak.

The unlimited ClubAcela is very interesting because the airlines do not give out club membships, they only discount them for elites.