AC/DC pack will include unique achievements
According to the Rock Band forums, one of the Harmonix developers has confirmed the AC/DC pack will include its own achievement list. HMXHenry wrote: "There will be unique Achievements and Trophies for the AC/DC Track Pack, as well as several that are song specific."
Now the question remains, will it add a gamerscore to Rock Band 2 during transfer or will the achievements only be available while playing from the AC/DC disc? We'll update you as more details are released.