During PAX East last week, Paragon Studios announced that City of Heroes players will have access to worldwide servers beginning later this summer. Devs have posted a handy dandy FAQ about account name "collisions" and how those issues will be solved for players.
3- What will happen if my European account name is the same as someone else's in North America?
We wanted to keep this process as simple and manageable as possible to allow European and North American accounts to access all City of Heroes servers. All European accounts with a name conflicting with a North American account will be prepended with an "EU". For instance, let's take a hypothetical European account called "Cityof". Pre-pended with "EU" would make it "EUCityof". That is the only change to account names in that respect. We determined that this was the lowest number of users that would be affected by this account name change. North American accounts with conflicting names won't be affected by this change.
Read more here.