No costs on BFL's side for a willing call center.  Outbound centers get paid per sale, in this case, for a successful issuance of a coupon code.  I would tend to think that the coupon code wouldn't be enough for the center to get paid, and that BFL would require the code to be used by the lead to generate a payout to the center.

On the center's side, they can add upsells such as cards for free gas and groceries, magazine subscriptions, government grant training (is that still alive?), identity theft protection, etc, just to have an income stream while the coupon hasn't been used.