i was at the dealer the other day and i questioned them about this.
i was told that its $1,500 off msrp. probably a lie.
i was also told that this is money that bmw NA comps the dealership. this leads me to believe that the salesman was being untruthful, and the $1500 is after you negotiate your price. i wouldn't allow them to include the $1500 in the negotiating. come to a negotiated price, and subtract the $1500 from that.