Ok, I think I'm up to speed now. To summarize:
Dealers are allocated a certain number of units per month to sell from their dealership. When they sell a car from their allocations, they're less likely to give you a good deal because they want to maximize profits from the cars they're allocated.
BMW may or may not allow individual dealers to sell above their allotted units per month. If they're not allowing a dealer to sell outside of allocations, and the dealer has sold their allotted cars for the month, a buyer will have to wait until the dealer gets more units in that they can sell. If they are allowing the dealer to sell outside of allocations, and the dealer has sold their allotted cars for the month, the buyer can simply purchase a vehicle through the dealership that doesn't come from their allocations. This is when the buyer is most likely to get a good deal.
But a question (if I have that all right): If BMW is allowing a dealer to sell outside of allocations, doesn't the dealer stand to profit just as much by selling outside of allocations? Why are they more likely to mark it down then?