I don't have any insider knowledge to this but just adding my 2c's.
The (relative) shortage of spaces in the centre would lead me to speculate that employees would be actively discouraged from parking in the centre. Any time that I have passed the centre during peak times (late night shopping/weekends) the car park info thing is showing almost 100% occupancy.
AFAIK the estates in the immediate vicinity are introducing pay n' display parking to stop free parkers. If I were in this situation I would find the nearest LUAS station with the best free parking and leave my car there, (Kilmacud Station would be a good bet, 1 stop from Balally/Shopping Centre)