With my 46/36/26 Sugino triple and 9 speed XT 11/34 cassette with 105 triple front and XT rear derailleurs, I can shift to and ride in *any* combination. And I don't get any rub in the front because I have barcons and the front is friction only shifting.

I typically don't though, 99% of my riding is on the upper 2/3 of the middle ring. I don't normally crosschain on the small or big rings, but I feel free to use every cog on the middle ring.

But if that LBS mechanic is worth his pay, he should be able to get that thing to shift to any combination.