I don't see how the U.S. could be sponsoring the lottery, though. My understanding is that the U.S. is generally willing to receive Cuban emigrants at all times, while Cuba places severe restrictions on emigration. If this is the case, then the obstacle to emigration would be the Cuban government, not the U.S. government; so it seems to me that winning a U.S.-sponsered lottery would be useless if the Cuban government didn't want the winner to emigrate. The decision is ultimately Cuba's to make; therefore it makes more sense that the lottery would be sponsored by Cuba.
That's how it seems to me, anyway. It's really an oddball thing, isn't it? Why do you think the Cuban government would allow such a lottery? My theory is that it likes having the dollars that the emigrants send back home. But what bad PR! What an admission that all is far from well in the workers' paradise.