Amtrak's entire policy is:
Folding bicycles may be brought aboard certain passenger cars as carry-on baggage. Only true folding bicycles (bicycles specifically designed to fold up into a compact assembly) are acceptable. Generally, these bikes have frame latches allowing the frame to be collapsed, and small wheels. Regular bikes of any size, with or without wheels, are not considered folding bikes, and may not be stored as folding bikes aboard trains. You must fold up your folding bicycle before boarding the train. You may store the bike only in luggage storage areas at the end of the car (or, in Superliners, on the lower level). You may not store bikes in overhead racks.
This guy claims that this policy specifically includes Acela's cars, which are the toughest situation. I think the Tikit will easily count as "compact assembly", though yeah, I imagine the Swift would not. But you probably want to check first. And cover the bike. For example this guy says he's been thrown off twice for having a folding bike.