Nokia in Greece replies that they have recently removed the USB break damage from the list of the ones covered by warranty! Obviously it costs too much.

The third-party repair shop that took a look at the detached USB port replied that iron-soldering it back is not an option because they do not have a clear view at the point they had to work on. Things are too crowded in there. This is the reason why they would not try to use 300 C heat either, since that might harm other sensitive parts (camera etc).

I will ask elsewhere before I give up though. Does anyone else besides maxximuscool has a success story of iron-soldering to share?