I can only recall one case where EU/NA copies alternated and it wasn't the norm.
It almost always goes NA for two weeks then EU for two weeks followed by EU remaining on the PTS until the next round of testing. They may re-copy EU but I doubt it.
I hope at some point they will do a NA character copy because I like using the PTS for testing my builds. What they really need is a NA and EU PTS servers so this doesn't become an issue. Plus they would get more testing because I would imagine that most people would rather test with their normal characters than the templates.