Over on Reddit, some questions are being answered by the EA Community Manager. A question was asked as to what vehicles and ships one can pilot in Star Wars: Battlefront.
The At-At, of course, won't be one of them but the Community Manager did let out that the Millennium Falcon will be one ship you can fly around. This is in conjunction with X-Wings and Tie Fighters. Unfortunately, it doesn't sound like you'll be able to take it into space, but at least you'll be able to pilot Han's piece of junk.
Star Wars: Battlefront is due out November 17th.