BL motors arent waterproof by design, though some people say they have no problems running theirs in the snow or rain. Personally I think the only good motors for that use are brushed ones, since they can be broken in underwater, so rain and snow isnt an issue.
They might be some what water proof. The wires have a varnish coat on them and the only part that doesn't goes to the end which they remove the vernish.