Depends on the book and its availability. I ordered from Dymocks once, and it took about a week for 3 of the books, and about three weeks for the other 3 (I know Dymocks is not A&R).
It all depends on stock. At Borders if you special order in, it takes between 2 and 4 weeks because they order from the distributor in the US if there are none in stock in Australia. Then it all comes down to how many copies the distributor has, locating stock, etc. I assume it would be a similar thing with A&R, but more automated.