Getting a ASCP DRP plan to recommend inventory rebalance with end-item substitution

I've been told many times over that a DRP plan will rebalance inventory while recommending and end-item substitution, but haven't been able to get it to actually execute this in our test instance. My scenario is simply that we have older superceded inventory that we have set up item substitution relationships for. This old inventory sits at distribution center A.  When forecast demand is created for distribution center B for item X2, we would like DRP to recommend an inventory rebalance of of item X1 (older item) from distribution center A to distribution center B to burn up the old