I don't think any of us are "positive" of anything...just throwing around speculations here. And we're not saying the transporter was for the sub itself...we're saying the sub is only short-range, and the people got to the Looking Glass via a freaky teleport doorway, and the sub just took them from there to the dock. (at least, that's what I'm saying) The people think they rode the sub the whole time, but actually didn't. (they were unconscious the whole time, like Juliet) We never saw the sub moving...just them on the dock walking away from the sub.