It depends what equipment he has. If its the top range stuff that can calculated the requested seed key then its possibleto read and write into the lowest level.
If you have a working system with key then its possible to write, but not read, so you would either get a already modified file and just load it in using the £15 range of interfaces (KWP2000 etc). You need to work a missing wire into the ECU plug to pull it high.
Alternatively get an unmodified original file and have the maps altered, then load it in.
The job offered sounds as though the guys have lists of mapped files and just load them - ie no proof that they are any good or any better than what you have, or any proof by road test that they actually improve things.
Just make sure that you have a .ori file on standby in case it all goes wrong, then you can just load it back in.
The ECU used is Bosch M1.5.5