Can't see this obviously spelled out elsewhere...
What about non-US, non-Canadian Mt.Gox customers, do their records and day-to-day interaction with MtG stay in Japan, or is everything moving to California...?
Non-US/CA customers have no change at all. All data remains here.
Since your statement is a little bit vague, I'm going to continue to assume that Mt. Gox complies with most or all subpoenas, court orders, and search warrants and honors all gag orders which might accompany them. Particularly if they come from Japan or a government with friendly relations to them. Please feel free to disabuse me of this misconception if you feel inclined.
Assuming that the conversation is supposed to be taken to mean transfer of information except those outlined above, it's not the protection of my identity information while Mt. Gox remains a viable entity which bothers me so much as what happens should Mt. Gox shutter it's doors.
Japanese privacy laws are actually stronger than the one you may find in other countries (for example USA).
If you want to know more about our privacy policies, you may want to
read them. Either way there is no way a company, no matter where it is located, would be able to go against an order from a court of its own country. This said, unless you are involved in some kind of fraudulent activity, there is little to no chances that your data would be ever the subject of a court order.