Some comments and some questions: First, the trainee controller does not seem like the brightest bulb on the Xmas tree. A simple reply like "You are at Bravo, not Alpha" would have been good. Second, as someone has already pointed out, the mistaken identity of the intersections was almost a weekly event, yet the supervisor left the trainee controller without supervision, and the airport authorities had not done anything in terms of signage to stop these repeated errors.
Now for my questions: What percentage of professional air carrier pilots would have backtracked Rwy 07 for a full length departure? An extra 400m is, well, an extra 400m! Also, was the crew's decision to use flaps 20 made early in the process, or was that selection made after the captain commented that the runway looked short? How much benefit was derived by powering up while braked? If this had not been done, how much extra runway might have been needed before the mains left the ground?