It's very easy to withdraw from MtGox with Japanese and Chinese currencies. BTCChina is very close to GoxUSD in terms of price. The MtGox price is actually pretty accurate, bitstamp is the one that is lagging behind.

So can you swift/iban jpy to your bank from gox and expect a good turnaround time?

Well you can withdraw to a Chinese/Japanese bank account in one working day.