Based on some fan captured footage from their show in Portsmouth, UK, legendary The Clash members Mick Jones and Paul Simonon are indeed on the rumoured tour with Gorillaz. The two reunited for the title track on the Gorillaz' new album, Plastic Beach, but both musicians can be seen performing on the track "Dare" in the aforementioned video.
The band has confirmed that Paul and Mick will be performing with the band on the rest of the band's rehearsal tour. That includes shows from the 22nd through the 27th throughout the UK