Yea, Google makes it easy.....

Did Tony Iommi ever play guitar with Tull?
Sort of. During the brief time in 1968 after Mick Abrahams left but before Martin Barre joined, Tull appeared on TV in a film called "The Rolling Stones Rock and Roll Circus." They performed "A Song for Jeffrey," though only Ian was actually live; the others mimed to a backing tape. Tony Iommi was the guitarist seen in this film clip with Tull, and apparently he nearly joined the band. Mick Abrahams recalls, "Tony only did the Rock & Roll circus thing. He phoned me up afterwards and told me he couldn't stand it - he quit straight after that."

I assume this is what you are talking about...  

Tony Iommi lost the tips of some of his fingers in a welding accident.
He has to wear some sort of prosthetic on the ends so he can play guitar.
The accident happened when he went to work on his last day on the job
after his mother insisted that he go when he didn't feel like showing up for work.
The next day, he was supposed to go on tour with Black Sabbath.
I bet his mom felt like total shit.

Quoted: Tony Iommi lost the tips of some of his fingers in a welding accident. He has to wear some sort of prosthetic on the ends so he can play guitar. The accident happened when he went to work on his last day on the job after his mother insisted that he go when he didn't feel like showing up for work. The next day, he was supposed to go on tour with Black Sabbath. I bet his mom felt like total shit.

I've heard about that.  What I read was that he tuned down his guitar a half step to make it easier on his fingers and that is part of what gave Sabbath their sound.  

IIRC, the original Tull guitarist was Mick Abrahams.  Rumors back in the day said Abrams was upstaging Ian Anderson, so he booted him out of the band.  Abrams started Blodwyn Pig, a GREAT band that I was fortunate enough to see live.  

Here's the first album cover...it's a classic.  (Actually, there should be red and yellow target background, but that's missing.)