No its more related to your shader.
Unity 3 does not cast realtime shadows from anything thats beast lightmapped.
Only the legacy lightmap shader will do that cause its a Unity 2 thing thats there for people and projects that upgraded, but its not halfway as integrated and feature rich as using beast.
Also if you talk about them not casting shadows in the lightmap → don’t make them static during the lightmap calculation
sorry if I went down the wrong path but your description is not exactly clear as you talk about self shadowing in the title yet the content you write has nothing to do with self shadowing at all as far as I see (self shadowing is indeed not controllable, either it casts full shadow or none)