It is great to hear that Maryland might get access for bikes on more trains. Here in California all in-state Amtrak trains and thru-way buses allow bicycles un-boxed. Last time I rode to L.A. from San Francisco, I took the San Juaquin route home and didn't have to box the bike. Granted half the trip was on a bus and took 12 hours to get home it was way more fun than flying. You can take Amtrak services all the way to Arcata or Ashland, OR without boxing the bike. (I hope Arnold doesn't take money away from Amtrak during this year's budget like he is talking about with the state parks)
Sadly on long distance trains that travel between states (California Zephyr, Coast Starlight, Southwest Chief, City of New Orleans, etc) you must box up bikes and can only use stations that have checked baggage. Luckily the Amtrak boxes are huge, just take the pedals off and turn the handlebars. So if the Xtracycle without the front tire is the same length as a regular bike you shouldn't have a problem.