[RSwank]

I have not seen exact "rules" for whether or not a MACR needed to be filed.
There are many cases when a plane "landed" or even essentially "crash landed" in allied territory on the continent (i.e. it did no return to England) and no MACR was filed. I "think" in all those cases no crew were killed or at least none were "missing". Also, if the plane actually returned to base with dead aboard typically no MACR was filed.

If the plane returned but some crew members had bailed out and their whereabouts were unknown (there are cases like that), then a MACR was filed.

It may be that the key concept is whether or not crew members were actually "missing", e.g. in the North Sea in the case of the collision discussed above, behind enemy lines or even possibly in allied territory but not immediately known to be under allied "control"