Select objects in a locked layer

I often create a background layer to contain objects that are shared between several perspectives on the same problem. To simplify working on the higher, overlay layers I frequently lock the background layer. However, when I want to move the resulting diagram to another document, the useful feature of locking the layer – that I won’t accidentally select and/or move the background – prevents me from selecting the background for transfer. Is there any way to explicitly override the “layer lock” without unlocking it? I had expected e.g. command select or some other key-mash to allow me to select the objects in the background layer, but I can’t find a way to do it.

Note – I understand how to “lock” an individual object. That would help when I’m read to transfer the diagram, but clutters things up when I’m working on it.