nipper, what do you think?
From here, this is pointing to the BIU. The BIU not only controls the lights, but also the tail & illumination relay that provides 12 V to the lighting circuit. Other than a short somewhere in the wiring, which I tend to doubt (although it is a possibility, albeit slight), it sounds as if the BIU isn't switching off the relay, thereby maintaining 12 power to the lighting circuit. But if it was just the relay, the lights should still be off because the BIU controls them on the ground side. So the BIU would also have to be maintaining that continuity to ground which would seem unusual (although this might not necessarily be needed to turn the lights off if the relay is open).
The BIU is the central "router" for the LAN and sensors. Almost all communications between the ECM, TCM, ABS, VDC, security etc systems goes through, and is processed by, the BIU. I never checked on this, but I wonder if it would be covered by the extended 5/60,000 power train warranty.
However, there's something I'm not clear about, and it's back to nipper's first question: which lights?
Miroslav: What exactly do you mean by "dashboard" and "instrument panel"? Is that what Subaru describes as the "combination meter", which is the part where the speedometer, tachometer, fuel gauge, and warning lights, are found, or do you mean the rest of the front area where the controls for the radio and heater are located? (Or is it both?) Also, what part of the radio is lit -- the knobs, or the display? I ask because the radio and heater knob lighting are the same circuit, so if one is lit I would expect the other to be as well.