The day ToS officially released I had planned to play on Klaipeda. However, when I went to put in my team name I was given the error that the name was already taken. I logged over to Orsha and I was able to make my team just fine using the same name no change at all.
I sent a support ticket recently since I was concerned about what would happen to team names already on Klaipeda when the merge happens. The response I received said team names are unique to the region of the servers. This would mean a name on NA can still be used on SEA. However, trying to use a name on Orsha that is already used on Klaipeda would not work.
It is possible this rule came into effect after the servers were assigned regions, but the response to my tickets has made no mention of this nor made any mention of what would happen should this conflict exist.

