I was told by the recruiting officer (not the HR) to expect further contact from him early in the new year. There has been no news so far. Would it be reasonable to send a reaffirming note of interest by Jan 9 to him?
Everyone is on vacation here and even for the rest of January things are sluggish. They haven't forgotten you if they interviewed you so it would be a waste of time. Unless you have an offer from another place. Then by all means try to contact someone.
I also know that the university has a 10 day period in which an offer remains valid (probably same for most Australian universities as far as I know). Therefore any offer made before Christmas must have been decided upon.
I doubt each college in my university has the same rules! Probably not each department even.
In the recruitment policy of the university I found out a statement which uses the term approving officer - would that be the supervisor/dean or the HR?
Again, could be anything. Here we have a term "delegated authority" which is the head of department or dean. But a different university could operate differently.