I tried running a Tektro BMX lever on my bullhorns a while back, and after a good hour of cursing, filing and forcing I managed to mount it on my bars. Scratched the bars all to hell, made me wonder how much I'd messed up the clamp, and frankly wasn't that comfortable anyway. Switched to a Tektro 'cross lever, and life was dandy. Until I yanked the brakes for good. And then life was dandier.

Also, as I understand it, brake levers intended for use with cantilever brakes work fine with road calipers (same amount of pull), but brake levers intended for V-brakes don't.