thank you very much. I just got the dog in a trade and its on my Soul Silver, so I can just migrate it to Black and pick up a Zoraaku.Yes. The flag that triggers the event isn't region locked, so any Pokemon with the correct flag will trigger the event for any version.
HOWEVER, the languages of the two carts you're transferring between does have to match. So if your Japanese Dog is on a Japanese cartridge, you'll have to trade it to an American cartridge before you could unlock the event.