When I use linked group as particles objects, the layer of the group is not used, so I can't change the layer of my particles. I've noticed that it is the layer of the objects in the linked file that is used.

to reproduce this :

1. default scene , select the cube, create a group "A". save the file
2. New scene, link the group A as an instance dupligroup
3. delete the cube, create a sphere. add particles to it
4. Pick A as particles. render. It works
5. move the sphere and the group to layer 2.
6. check only layer 2 visible, check only layer 2 in the render layer visible, too.
7. Render, the particles aren't there

I noticed that particles visibility relies on groups (or object) layer and not its emitter layers, that could be a more logical workaround to modify this. The viewport behaviour relies on emitter, it should be identical.

tested with r38019 x64 and r39169 x32, win 7 Q6600