Can't find anyone that has tested this out or even been able to confirm it YET, even master GOOGLE is unable to help
"Given my understanding XX1 runs the same 1:1 actuation, i.e. cable pull distance = rear mech movement distance, so when paired with a 10speed 1:1 shifter it should operate identically to 10sp rear mech. Granted there will be minor adjustment with the b-limiter to ensure you dont have jockey wheels knocking on the 11t inner, but theoretically it should be functional! "
cable pull ratio, does not determine compatibility, unless the cassettes are teh same width AND the same number of gears. 11 speed is the same total width but closer together - ie narrower chain. Thus if the deraileur is 1 to 1, then it should be able to be used with sram 10 speed - though its too long and a different design entirely so it shouldnt work too well.
Shifters wont work because the amount of cable they pull is y divided by 11 , not y divided by 10.
so front crankset will work with 10 sp, rear deraileur should kind of work, shifter definately wont work well.
btw, anyone who wants greater than 45kmh offroad, can bloody have it (32/10at 120) - i'm thinking about brakes at that speed, not bloody pedalling