Well, they are in a sense. I know that Sun King and Mean Mr. Mustard are one track and Polythene Pam/Bathroom Window are one track. Not sure about Golden Slumbers and Carry That Weight, but it might make sense.
However, if you buy Abbey Road as an album and not just individual tracks, you get to play the medley complete which I'm guessing will be its own track. If you have a Wii, it remains to be seen how this will work, since Wii users currently can only buy individual tracks in the Rock Band music store.