I'm glad you've brought that point up, as this is something I've been wondering about for a while - do ECU controlled diesels do this as well as petrols?
Would my Lynx engined 1.8TDi Fiesta (75PS) do this (i.e. use zero fuel due to a cut-off switch/relay on deceleration).
In response to DervBoy - I make myself benefit from the lack of much engine braking by being able to come off the acclerator earlier on approach to junctions as I know it'll decelerate less. This has surely got to be saving fuel. It also means that if it has slowed down a bit more than I wanted I can just gently press the accelerator pedal again, without having to put the thing back in gear.
Peter