How to get discounted priced items for a given promotion

[anstuff]

I need to implement a feature where in I have to display all the products with discounted prices for a particular promotion.  Is there a way I can do this?
I have retrieved the promotion using getPromotion method of admin api, it seems to have applicableProducts which is an array of AdminOrderProduct.  But this array is always null. 
The hard way, I could get all products based on categoryRule and productRule but that will not have the discounted values. 
Suggestions well appreciated.