Yes it was done at the service last year, I didn't have a choice IIRC as I was advised it needed a "system update" to be done at that service. I then was told when I picked it up included "some throttle settings and other engine tweaks" and took about 3hrs to run...
To be honest I haven't noticed any difference, the car was only a year old with about 8k on the clock when it was done, it's now just over 2yrs with 18k and is loosening up nicely IMO. Currently returning 42mpg on the latest tank and about 48mpg average overall (using Trip A and B respectively).
Mine's the 1.4 petrol though, how the diesel cars have been changed (which is what the main VAG scam was about) I couldn't say.
2015 500X Pop Star, 1.4