At the moment you have it operational everywhere (though at some junctions in partial interim configurations) everywhere except the Bury line and Altrincham line, current schedule is that Altrincham line would be done next and Bury line would be the last to rollout.
PIDs were installed on the Altrincham line in 2008 because thats when the stations on the line were being refurbished and changed from blue livery to yellow livery. Bury line followed later and Eccles line had a more limited refurbishment mainly a repaint as it wasnt as old. During the refurbishments they also installed cable ducting for the future smartcard reader rollout alongside improvements to CCTV, platform comms (moving from a dialup phone system to internet packet based comms) and other improvements.
The old system for platform announcements being phone based had a limit on how many stations you could simultaneously announce to and each additional station added reduced the audio quality.