Interesting thanks for the thoughts David.
Today it is overcast, but with still quite a large difference inside-outside, I had trouble trying to repeat this issue taking the same shots and again exposing aggressively for the shadows I didn't get a green line in any of the shots.
Bit puzzled, not really sure what to do about it (if anything) Obviously if it starts to show up in real world day to day shooting I will get it serviced.
I managed to get a another green line/s so I guess I will have to send it back to Sony (this means every DSLR I have bought since 2006 has had a problem of some sort, (1 x Km5d black frame, A200 returned twice dirty VF, K-x with mirror slap problem, K-r front focus, D90 x 3 back focus, D7000 x2 back focus, A57 apparent sensor problem) I find that staggeringly worrying..
Anyway here's a few more green line shots.