The issue with the Pocket Rocket is that with such a big fold, you will be totally at the whim of the conductors. Some will see your bike and embrace you like a long lost sibling... others will see your bike and will give you the evilest of evil eyes. If you give that second group any excuse, they will not allow you to bring it aboard as carry on baggage.

Things may be better now (haven't been on a train in 3 years since I moved to Utah), but I used to regularly travel Amtrak with a Tikit in the midwest. About one quarter of the time I had to pull out my copy of the policy and explain it to the conductor. While I was always able to prevail... there were a couple of times that I was afraid I wouldn't even be allowed on the train.

My suggestion to you is to try and find a way to make the Pocket Rocket as small as possible... or put some portion of the bike in a duffle bag as has been suggested above.