Company of Heroes: Opposing Fronts
Ironically, the best way to find out is to try at this point...
The reason being is that Relic no longer really exists, and they are merely an extension of SEGA at this point. That being the case, they are vehemently anti-community and anti-modding, so between SEGA's/Relic's stance on modding and Steam being a bit of a flaky unknown on their support, I'd only be able to say:
"give it a shot, but don't expect too much"
If it works, wonderful, but I honestly don't have overly high hopes for it.
The current state of things is not really that good... The developer, Relic Studios, was bought out by SEGA, and both are notorious for screwing with the modding communities of their games, but SEGA especially has made concerted efforts against modders of their recent titles like the Total War series (SEGA also bought up Creative Assembly, the developer of Total War).
If I can, I will tinker around and hopefully make some fun things for COH2, but I can't make any promises.
In the "main support" thread of Ewiger Krieg found here:
grandovan, great guy and long time supporter of Ewiger Krieg, fiddled with it himself and has confirmed it working for me, so give it a go and if in doubt check the Steam COH message boards as well, for fellow Steam-COH players who've enabled their mods.
So - put all ewiger folders to directory with main data of Company of Heroes RELUNCH!where the .exe file is in steam apps directory. In Steam library of the games right click on the game, choose options and there is something like "start option" - to this next empty box feel free tu put exactly -dev -mod Ewiger_Krieg and you should add -unlock_all_missions (it will unlock all missions). Just one line, keep the spaces between the words. Between -... there is no space.
So just try - for me it works perfect.