The band are managing to keep their heads out of the local media surprisingly well. Aside from jumping up on stage with Kylie Minogue on Sunday night, the only publicly reported sighting of any of them was Bono out on the town on Saturday night (well into Sunday morning). I guess it's because they are not staying in hotels in the city, but in rented homes down on the harbour, and that they have flown all of their extended families into Sydney for the week, so are probably mostly keeping their heads down and hangin' with them. So no, no reports of them being in the studio on Sunday, but it makes sense. Sydney is the stop on this leg where they are spending the most time (a full week), and they were booked into the same studios for the week preceeding the original kicking off of the Australian leg back in March to do some stuff with Kanye. This could easily have been their first opportunity since then to meet up again, so could easily be happening. It might be exactly why the band seem to be off the radar during the days here in Sydney.