There is none. I've been asked that question several times, and I asked Plarium twice or thrice (once quite recently, to check if it changed over time). The answer was always no.
I was once told that it'd be unfair to bring a fully grown haven instead of growing it on the server. I must admit I do see some potential for abuse, which I'm guessing is why Plarium won't open that Pandora's box.
Or is it like .... they want to keep it going with thousands of fake havens and force the servers to stay alive(dont let the corpse rot!! 😂), where the revenue comes from ... untill, they are ready to
... boil the sea ?
well, that's just boring for real players in every way. They can't switch to more populated one, neither the servers would merge. Hoping to see some interesting suggestions.