I'm pretty sure that all non-UK stations normally air things a week after they are aired on BBC, it just happens that the first episode of this season is bumped forward a bit for BBC America. I'm not saying this isn't weird, just pointing out that this happens for everywhere, not just Australia.
IIRC, BBCA aired Doctor Who the same day as the BBC last season. That hasn't been the case most years past, though. As far as I can remember, the "one week behind" thing has been the norm, at least for Doctor Who.
Since 2005, months at first, then weeks by the time series 5 rolled out (though the End of Time was only one week behind).
A Christmas Carol was same day as was all of series 6. Indeed, the need to go online for new Who has decreased. (Although I would buy the season sets when they became available to pay my dues to ensure more were made).
Back during classic Who, a few PBS stations aired some late season 1980s stuff before the BBC due to special agreements.
