I got this from BA a few days ago:

Pay no commission on Travelex currency transactions in the US and earn BA Miles.


New for our Executive Club members in the US: You can now earn BA Miles for every foreign currency transaction at any Travelex location in the United States and arrive at your destination with local cash. It's simple; just visit any Travelex stores in the US and earn BA Miles for every qualifying transaction. Plus, take advantage of our introductory offer: exchange your currency before your trip and pay no commission* when you transact until January 31, 2006.

Travelex, the world's foreign exchange company, carries all major currencies including British pounds, Euro, Japanese yen, Australian dollars, Canadian dollars, Swiss francs and Mexican pesos. For additional information and terms and conditions, please click here.

* This special introductory offer is available now through January 31, 2006. Executive Club members pay no commission on currency and travellers cheque sale or purchase transactions.

It seems to me that this works for money that you convert and spend, which is obviously their intention. Is there some way to exploit this simply for miles? It looks like the offer doesn't apply to travelers checks. If you exchange and then exchange back, you lose the "spread," which is substantial. And if you lock in the re-exchange rate, I don't think that you get the BA miles. Any loopholes, all you geniuses out there?