I think, that al least temp data sends by canbus, because in mustangs with climate control this data uses to control em... climate control ( :) )
And I'm sure that I've saw clock data within cabus messages, so temp data should be there.
I've tried sniff messages from removed front panel...... and there is one issue..... panel's controller waits some "special message" from "some special" module to switch itself on.
I know only one way to avoid this, use 2 canbus controllers, one connect to car's bus other one to removed module e.g. build some kind of network router.
About ignition, you can choose any of message which appear in your log when you switch ignition on, even if it only switch main cluster illumination on :)