I don't know the actual ingredient list of Subway dressings, but it seems a safe assumption that they are industry-standard. With that assumption in mind:
None of the fat-free or "lite" dressings come close. These almost universally replace fat with corn syrup. Almost any sweet tasting one is sweetened with corn syrup too--even if it has "honey" in the name....
Probably none of the rest of them come all that close either, since virtually ALL commercially prepared salad dressings and mayos are made with canola, soybean, or other seed oil. Even the "olive oil" dressings almost always contain a blend. This has been the source of much irritation for me--i literally looked at EVERY TYPE of dressing at several markets and could not find a single one--even at Whole Foods--that was made with 100% olive oil.
I realize this doesn't exactly answer your question. I suppose my answer is that it makes no difference which dressing you choose--they all have the same paleo strikes against them.
As a possibly vexing alternative, you could get into the habit of making your own and bringing it with you or keeping it in the fridge at work, etc. Not something I choose to do myself, but some people do.