The E-3D is not an MPA aircraft but its paid for and can provide more than just early warning, the MRA 4 was a 3.4 billion cost saving to the bean counters nothing more.
As I understand it the money has been paid, therefore this decision will not save 3.4 billion.
And just to highlight this again, as I'd be hugely ietersted in seeing it answered should anyone reading these boards be in a position to ask it publicly.
Please, do not ask the Defence Secretary, Prime Minister and anyone else who cares to listen, why there are currently several foreign MPA deployed to RAF Kinloss.