They basically took the place where 100k people were imprisoned, brutalized, tortured, and experimented on by a mad AI... hosed down the walls a bit, put a fresh coat of wireless inhibiting paint down on the new wi-fi blocking drywall, and started chucking in everyone who was too poor to say no to free (horrible) food, free (vending machine) clothes, and free (prison style) housing for the rest of their lives. The floors they did turn over were the ones that were largely the mazes, zombie rooms, and 'medical' wards under Deus.
Oh, and they never cleaned out the old hardware since it's, well... required to run the various arcology systems. There was a short fiction blurb in one of the SR4 sourcebooks where a technomancer went into the system and was almost instantly tossed out because 'it's full of ghosts!'.
And still, folks are signing up to live there. The admissions line is so long that they have multiple in-processing locations (but no out-processing, of course). It's 100k full again and still more arrive.
It's the Barrens-in-a-can, and the can isn't so strong as it used to be.