Issues with linked objects and layers

I have a game made with one central file and a number of other files containing assets used in the central file (weapons, props, effects, vehicles, you know the drill). These are all linked into the central file into the scene where the game takes place, but are kept on layers that are not visible.
When the scene is set to the game one, the linked objects usually all appear in the scene even though the layers they are no are not visible, why is this?

I’m not sure as i’ve not done it yet in BGE… But I have in normal Blender, and the new API defaults to insert on the current layer (and make selected), maybe you need to alter the import line?

Is it possible to see it?