All Audi centres are linked to a computer system called DIALOG, which to be honest is very old and not much good. It will only tell you when a particular car was last serviced by an Audi dealer and who carried out that work, it will not tell you exactly what work was carried out.
The dealer can bring up the service history regardless of where it's been done, but for any other dealer they only have a basic summary, not the full details.