The Hot Bat buses will only be connected to their respective Battery Buses until DC 3 is powered. Doing this energises the Battery Transfer Relay and de-energises the Battery Relay. With the Battery Relay de-energised, the Hot & regular bat buses are divided.
Well, I thought the items you mentioned would keep you busy : ). I have a long list of items affected by AC 1, but not handy at the moment. Of course, there are variations between different versions of the -400, including engine type differences.
From memory, I recall the C IRU will be running off one of the Hot Bat Buses, but won't cut out after 5 minutes like it does when you're running on Standby Power only.
Cheers
NSEU.