In the draft list they are described as:
Stakes carried by Burgundian or English longbowmen - PO @ 1AP
So IMO 0-1 per Bw(S) tells you how many PO you can have, but the description says they can be carried by any element of longbowmen (which would include Bw(X) with longbows).
Even if it was the rear element that owned the PO, setting them up is a move ("1 PIP is expended for:...Each time and element uses a move to set up PO."), and DBE count as one element for movement, so IMO they could be set up in front of the DBE.