It appeared in a large number of articles about the game when it was first announced. Here's just one of them, and the quote that mentions specifically that it was not to be a Rock Band named game initially...
"LoPiccolo, the Harmonix vice president, added that while the Beatles game will not be branded as a Rock Band game, it will be similar to Rock Band in some respects; it will also have new features specifically developed for the Beatles' music."
Great to hear Dhani's interview regarding the game.
While I would like to be able to export the game to RB, I'm not really worried about it. I fully expect that it won't export, and I can understand why - it's not really up to HMX. There are others involved with this, and I'm pretty amazed we even have the game coming out. There have been lawsuits and disagreements for years regarding various issues. Wouldn't take much to have the Beatles, Apple, etc. want to avoid the export.
As somebody who has listened to The Beatles since the 60s, I'm not the least bit concerned about playing a single band. The Beatles sound changed so much over their career, that it's not like you're playing the same single song type over and over again. Having DLC for the game would be a really nice bonus though. It would keep the game interesting, and definitely will up the interest for some people who don't see some favorite songs on the initial set list.