The box circuits, blocks, etc between Proof House and New Street No.1 / New Street No.2 were in cables on the Midland side, out of shot to the left. Those wires were fed from a cable which went up the brick pier between the Midland and LNW sides. I think they may have been the telephone trunks between the New Street and Snow Hill exchanges.
The foot of the ladder is certainly foul of the Down London line. I'm not sure who the man in the hat is, but he may have already appeared in post #10 of this thread.