Perhaps it’s to do with reduced need for standby controllers to cover sickness or sudden incapacitation or simply breaks?
Hard to see the savings from that to be worth it though.
Or maybe they feel it would be a good location for testing the technology rather than it being an efficiency thing?
It’s probably cheaper to employ controllers in Swanwick than London (which is an absurdly expensive place to live, and employees often get premium pay to afford the cost of living).