It seems that the band has reunited in the studio of Hanover Quay in Dublin. A source would have talked to Dallas on Saturday and obtained confirmation. See what the site says U2 place today:
News posted today, April 23 at the Italian site U2 Place:
Some rumors from the forum Interference speculate the presence of U2 in Hanover Quay, a user wrote that he received word from a friend who is in Dublin. According to the news in the late morning of Saturday, Dallas would have confirmed the presence of U2 in the studio stating that at that time had gone out to lunch. But probably not return to the studio in the afternoon.
During the weekend, there were some photos and stories from fans on Twitter that Bono was in Dublin after his private trip to Israel. We will be alert to any news and so the news is coming, we will post here on the site!
In an article in the Irish network RTE site, Norah Jones was asked if the producer Brian Burton (Danger Mouse) - who worked with her on her new album - said something about the work with U2. The singer evaded and refused to give details, but revealed that Burton "told many things about it (U2 album)" but that there was "nothing she could tell a reporter from Dublin."