As it is explained to me by my employer the problem lies with SACL as they won't play ball on the staff bus issue. I guess they think the increased bus service will mitigate any problems.
Both BNE and MEL have dedicated staff busses seperate from the general public. Don't know the reason why they do but Sydney doesn't. There is a staff bus for Intl at SYD from the Long Term just not the Domestic.