Although your post was moved here, it probably belongs in the United forum. While there are lots of Amtrak experts here, I think most of the expertise about the 2V/UA program is there. There is a topic there dedicated to the Amtrak/United codeshare program.
The Ultimate ZFV (Philadelphia) / Amtrak - CO FAQ
EDIT: The linked topic was started in 2004 and some of the early info may be out of date.
Last edited by NovaEngr; Jun 8, 2013 at 8:07 pm
Reason: Added info about the linked topic.