Hi!
I can't see you having a problem with writing on a train. I used to work in London, which was an hour's commute by train, and I wrote or worked every day on the way in and the way back from work. Train's these days tend to have power outlets for you to use, and I'm figuring that's the same everywhere as I've travelled in Europe and seen the sockets.
I found it much easier when there was a table, but that's only because I like to have a printed outline / scene notes / bios on hand as I write so I don't have to flip screens between my writing and my outline and scenes. Editing is much easier as you can do that with the computer on your knees.
A netbook would be good for it as they're uber lightweight, small, and have long battery life if you treat them right.
The downside is that you're not going to be seeing much if you're writing whilst travelling, unless you're only interested in seeing the places you stop at rather than scenery along the way.
Felicity Heaton