Yes...Long-eared will eat Saw-whets.... but really depends upon winter and food supply. Generally owls do not actively hut each other unless food supply is low and an opportunely presents its self. LEO, SEO, NWSO prefer mice , while Barred owl like more snakes, frogs & mice, GHO prefer skunks, rabbits and bigger game ....but all will hunt small owls in right conditions , also hawks will also take the small owls.
As both LEO & NWSO preferred the denser cedars and pines groves, it is possible to find both in same general area in winter, but doubt you would find in same tree.