The clearest indication yet that Coldplay will be performing a duet with Jay-Z at Sunday's Grammy Awards has come courtesy of arjanwrites music blog.
Today, Radiohead (with USC marchind band), Coldplay (with Jay-Z) and U2 are rehearsing. U2 will open the show tomorrow with their new single. Unfortunately, all of these bands have explicity requested that no audience, media and Academy staff members are at their rehearsals, so I can give you updates about that. But Radio will be super cool no matter what.
More on this at the Coldplay forum here [thanks mimixxx]