I posted once a simplified example of how arbitrage can work smoothly between the Chinese and Western markets without ever exchanging CNY x USD.  One needs  accounts on both exchanges (which any businessman with a foot on each country could get), or a society of two who agree to share the profits.

And it is a fact that all the markets are well-connected so that the prices are closely matched, except briefly when the price is swinging too fast, and with adjustment factors presumably due to fees or other reasons  I beieve that it is arbitrage, in fact, that eliminated the "free fall" crashes that used to be common months ago, and has turned them into slower "viscous" falls.

The unity of all the markets became notable when MtGOX severed both the money and the bitcoin channels with the rest of the world.  That is the sort of divergence we should see if China and the West were really disconnected.