It's not much of a secret at this point: U2 is moving into the Pacific Coliseum in Vancouver (a second indoor arena in the city) for rehearsals prior to the start of the Innocence + Experience tour on May 14th at Rogers Arena. Local media outlets have been scouting the scene at Pacific Coliseum since the start of the week and generally finding nothing more than those red/white Upstaging trucks in the parking lot -- trucks that U2 fans have seen before on previous tours.
U2 fan Jonathan Vervaet (well, his wife, actually) paid a visit to Pacific Coliseum on Tuesday night and heard what sure sounds to us like a live U2 rehearsal, complete with Bono singing. It's a brief clip of "Vertigo" with the music really kicking in at about the :20 mark. Have a listen.
There's a chance that this is pre-recorded audio and the crew is using it to test audio levels and equipment. But the way the song stops leads me to think otherwise. You can decide for yourself.
UPDATE: Jonathan has uploaded more than one clip from Tuesday's rehearsal. Here's a longer take on "Vertigo."