MTV Games and Harmonix have issued a statement that says they are working hard to get the microphones bundled with Lips to work with Rock Band and Rock Band 2.
With any luck this means that owners of both titles should expect to see a patch arrive in just a few short weeks.
Source
“Microsoft and MTV Games are working together to ensure that consumers will be able to use the wireless mics from ‘Lips’ with ‘Rock Band 2’ after launch,” said the companies in an e-mailed statement. “More details on timing to come. Harmonix and MTV Games strive for all third-party controllers to work with the ‘Rock Band’ games, fitting with Harmonix’ open-platform philosophy for controllers.”
With any luck this means that owners of both titles should expect to see a patch arrive in just a few short weeks.
Source