Alfred,
You imply that there's a pot of gold with 'MPA capability' written on the side of it, ready to be transferred to the Service with the best argument.
I don't think that's the case at all - post PR11, Defence had a set of outputs which did not include MPA, and PR12 has shown that there is still insufficient money for those outputs that PR11 did include.
Thus, there ain't no money to fight over.