I've spoken to one of the bods that I contract with and as far as he is aware, once a phone has been barred, it is blacklisted from all european networks and there is no easy way to get it removed from the list if at all. If you are thinking of trying to get it unbarred, I'd talk straight to the provider you use and see what they say. I'd say you are not going to be so lucky
Basically the bar is applied with the IMEI number, which is like an IP address for your phone. It identifies your phone uniquely and gives the details like model and make and also a unique number. They bar this and unless you change it it wont work again. Changing it is highly illegal from what I understand.
The network will also not give you any details of why the phone was barred. They dont know who the hell you are, so wont give you any info. They probably wont even be able to tell you its barred tbh, call centres probably dont have access to that information.
Bit more info on IMEI and barring: http://www.crimereduction.homeoffice.go ... goods5.htm