Can someone please confirm that it's not possible to set this up in MRP? If Location A requires stock, take it from Location B if there's stock in that location. Otherwise, raise a PO in Location A. It appears that the supply source is either a TO (through Planning Rule Group) or a PO/WO but never both for a particular location.

Following

I would agree that is not possible. The rule triggers the transfer order and also pushes the PO to the transferred from location.

Thanks