From US billing department:
If you purchased a copy of World of Warcraft from the North American
release (the US, Canada, Australia or New Zealand), and have NOT successfully created an account in that region, you may be able to transfer the authentication key to the European release. Please follow this link for more information:
http://en.wow-europe.com/Wowsegform/webform.aspx. If you have already created your account it cannot be transferred.
So i sent mail to EU department:
Response...
Hello,
If you allready created an account you will have to wait until after the release to hear about the announcment regarding transfer of accounts between servers. The details have not yet been finalized. aka Gwynbleidd (in CB since push1).