No they aren't.
Its up to the programmers of the teams to create "patches" which you will then download from XBox Live, that will make it compatible.
Thats because of the large hardware difference in the graphics hardware of XBox -> XBox 360
Its up to the programmers of the teams to create "patches" which you will then download from XBox Live, that will make it compatible.
Thats because of the large hardware difference in the graphics hardware of XBox -> XBox 360