Select curve objects by extrusion profile object

Hi,
I need to select all curve objects in my scene that have their bevel geometry set to OBJECT and share the same “extrusion object”. Or do it in the “reversed” way - first select a curve object that is shared between multiple curve objects as their “extrusion profile” (bevel), and then select those objects.
Either of the above will satisfy me.

I guess that would be a simple script, but I have no idea how to define the property: “curve object’s bevel object” in python. I could then type the profile object’s name as the property value.

Can you help?