Well, after some time I think I managed to almost replicate the effect in UE4. There are geometry pieces on the corners with translucent material applied (not decal). One issue that still persists is some kind of a light leak in shadows. Looks like that material does not fully accept shadows and still gets some highlights (roughness is 1, spec is 0, so it’s not specular highlights). Any idea on how to fix this?
Btw, I tried your solution enabling Cast Volumetric Translucent Shadow but then those pieces seem to only cast shadow, not accept one.