This is what I've got:
Hot Battery Bus
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IRS emerg. power
Landing gear alt. extension
Park brake valve
RAT manual deployment
APU fuel valve
L and R engine spar fuel valves
Fire extinguishing bottles
Clocks
Alternate refuelling system and quantity indication
Ground crew call horn
Battery Bus
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APU DC fuel pump
Engine fuel valves
Crossfeed valves
Normal fuel quantity indication
Inboard antiskid
A/G logic
Gear position indication systems (norm and alt)
Pax oxygen deployment
Engine HP bleed valves
Right pack valve
Wing and engine anti ice
Interphones
PA
Right thrust reverser
Standby engine instruments
Engine starting
Alternate equipment cooling
Engine, APU and cargo fire detection
Alternate stab trim
Hydraulic PTU control
L + R engine hydraulic pump shutoff valves
RAT auto deployment
Cockpit dome light
The diagrams I've got are undoubtedly simplified for us thickie pilots but from what I can see, with the HDG online you get AC power to the left and right AC transfer busses and Cpt flight instrument transfer bus. A transformer/rectifier seems to connect to the hot battery bus, so I would imagine if the batteries are flat then you would get hot battery bus, battery bus from the HDG and standby DC bus (assuming the standby power switch is in an appropriate position). I'd be nice to know if some more robust information correlates with that which I've been provided with over the years...