I have an EL buck...so far he hasn't started any fights, but he's just reaching his "Teenage stage" and so he's getting the hormones starting to kick in. If he had the chance, he'd probably fight a buck, but that won't happen unless it's an accident or he figures out how to break open all the bunnies in the barn...which would horrible.
Anyways, It's best to seperate them once they begin to reach puberty. Until then, you may want to keep them together. I know FallingStar has two does and they get a long great. She's not even sure if they're litter mates or from the same breeder, but they are just dolls and they love eachother SO much. I haven't seen them fight yet, but then again FallingStar and I aren't sure of there age. Once they hit puberty, though, it may be a different story.
Good luck! You'll love your English lop boys! A word of advice: THEY ARE WILD!
Emily