I guess the same applies to all mods. The other player must have the exact same mods as you do in order to play Multiplayer Campaign. You'll see, that if you host, or he/she does, that his/her and/or your game is the only compatible one to join. So yeah, in theory you should be fine both playing Multiplayer Campaign with the Radious Total War Mod.

Yep UltimateTobi is right works just fine in co-op if both players have the latest version of the mod.

yeah!!

A quick question. Tried yesterday to play rome 2 with a friend where we used radious total war mods. I got all the mods and he did to except for the radious battle mod. So we took it off and then tried again. Not possible to join each others game. Even if we only had the unit mods on. Dont know if radious battle mod makes it work. But i've tried to join another players game where he also had all the mods, and it dident seem to work. All the radious mods we downloaded from the steam workshop.