No not yet. The only way so far is that we can join the same empty server, but a stranger almost always also joins, and we're not trying to play mods or anything really outside classic zombies.

Even with my friend added on the plutonium forum, it won't let us join each others lobby. We got plutonium because it was doing the same thing when we tried to play through steam. We're just trying to play custom games together, not with randos. Any advice would be greatly appreciated.