As for Subway, I can identify the restaurants by smell alone from almost a block away, 100% of the time. There's no other smell on this earth quite like it (although I think it's the bread baking, not the pizza). Does anyone else know what I'm taking about here? I have a keen sense of smell, but it's not *that* sensitive.
With no evidence to back it up, I've always believed it's an artificial smell meant to evoke bread baking, not actual bread baking. Something "cooked up" (ha ha) in a lab somewhere off the New Jersey Turnpike.