Originally Posted by
jackal
No, they do not; they receive the "coupon lifted" transaction in Shares roughly 1.5 hours after the train departs PHL. That equates to roughly 30 minutes after the train arrives at EWR. Given that UA's system imposes a very lengthy MCT for EWR rail-to-plane connections (90 minutes?), there is no danger that the "coupon lifted" message will not come through before the flight departs EWR.
Note that Amtrak's system may assume someone is a no-show if you do not have your ticket scanned within a particular time after the train leaves PHL. It's very possible that this won't happen before the train arrives at Metropark, but it's a risk to not board in PHL and have your ticket scanned and lifted upon departure there.
This is interesting information, and I believe something I experienced last Summer. I boarded in Trenton, had my ticket scanned, and when I got to EWR to check in at the kiosk got a message to "see agent." The AirServ agent at the PremierAccess counter was kinda clueless and said the message on her screen indicated I missed the baggage cutoff and I needed to run to the gate. I bolted out of there but was ready to show my Amtrak boarding pass as proof just in case.