That means trains will leave from both of the station's platforms in alternating departures every five minutes, a system to be put to its first big test on February 19 after the Super 15 rugby clash between the Auckland Blues and Canterbury Crusaders.
Resignalling Quay Park through to Britomart, which KiwiRail deemed the most challenging of a range of construction tasks, is also critical to the electrification project.
Auckland rail upgrade director Peter King defended the unprecedented scale of the shutdown, saying it had enabled crews to get far more work done. "Trying to do work with trains whistling past every 10 minutes is just impossible," he said.
"We've been able to achieve a huge amount, and a lot of the work to tidy up the track and get it to a reasonable state hopefully means we've got a network that performs pretty well over the next 12 months."
The summer programme has also included the erection at Newmarket and Baldwin Ave Station on the western line of the first 45 of 3500 power supply masts needed for the arrival of electric trains in 2013, and the construction of more than 300 mast bases at various locations.
Work will continue until the end of January on a replacement station at Baldwin Ave, bringing its two platforms closer together and making them long enough for six-car trains.