Online Travel Booking and Bidding Agencies - UA cheaper through 30th St Philly

UA has much better fares from EWR when you start your trip at 30th St. Station in Philly and take the train?

Does anyone know how the ticketing works? How do they know you actually took the train to EWR?

Welcome to flyertalk.

Check out this long thread, though the first post addresses your question

http://www.flyertalk.com/forum/continental-onepass-pre-merger/374107-ultimate-zfv-philadelphia-amtrak-co-faq.html