I don't believe the power steering thing, why should it scrub tyres on the inner, its just a pump that helps you turn a mechanical mechanism. My 75 has power steering and never scrubs its tyres even at the very last of the 15K miles that I get from a set, I have the tracking set every 5K (fully laden like the manual says..).
My first 16V did 10K on its new front tyres and they were perfectly worn, again I had the tracking set regularly, and there was plenty of tread left after 10K
I would say if it is scrubbing tyres, somethings gone wrong. I've done about 1K miles on a set of Pirellis on the current 16v and so far so good.