They dry milk in totally different, specialized plants. I've seen this firsthand. I'm dan lekaf zechus that when you say they dry milk on the same equipment that they freeze dry coffee you're trolling.
re apple juice - a certain national brand apple juice (with an unreliable hashgocha) was made for years on the same equipment as clam chowder. I wouldn't be comfortable with that, would you? Minute maid had reports of being verified to only process Orange juice, nothing else, if that's really tue, and still true, and I had it from a reliable source, then I would be ok with that, personally.