If you are considering roof tiles in a bushfire area I would suggest you do not go above BAL Low.
If you decide against my recommendation I would advise you to only use a flat profile tile and when I say flat I mean dead flat as these have way less chance for entry of embers to the roofing materials.
However in saying that just remember you will have at least 2,000 independent tiles on your roof, any other profile I would stay away from as roof tiles are in no way perfect where everyone is exactly the same as the other. Some will have dags of material on them allowing them to rise up above the other for possible entry of embers.
Due to the added expense to make the tile companies comply up to BAL 40, I believe the cost alone for roof tiles in a bushfire area would be extremely extra ordinarily restrictive.
In a bushfire area you are much better off with the much lighter weight product of corrugated colorbond roofing, not only that there is nowhere for embers to enter, a much better chance of your property staying intact and a lot less worry.