It's easy bro.
Simply copy the sga-map archives from your EF-folders folder Eastern_Front\Archives to My Documents\My Games\Company of Heroes\WW2\Scenarios.
The only problem occuring is that mysterious purple or yellow blocks appear instead of Eastern Front's destroyed soviet tanks or vehicles. You can solve it, when you extract the sga-archives and open the sgb with the WorldBuilder and delete the purple blocks/vehicles.
You may edit the Scenario name too, because EF youses keys for their maps and archives just like Relic did, cause if the map is loaded ingame, there may appear either something like $123567_nokey or some text that has nothing to do with that map.
Have Fun!