I'm not sure where the boot release solenoid is fitted on a Sedan (as I have a Crewman). On some cars it's mounted on the boot lid and in other cars it's mounted on the body and attached to the boot latch with a stiff wire.
The solenoid should look like a small round cylinder - assuming the Commodore solenoid is the same as most other types......
Since fitting a Mid level BCM for the windows and getting new 3 button remotes, I now have a boot release function but obviously no boot to use it on. I could however use this boot release signal to operate something else - dunno what yet, still thinking about it.
I don't know how far back the wire runs in the Crewman loom but once I know the colour, it'd be easy to find.
I can hear a relay clicking in the BCM when I press the boot release button so the feature is working but I don't know which wire it's on and metering each wire looks like a right pain but I might have to try it.