There is no guarantee that the school you want to use have the CBIR. An ATO is a private company and they can choose what courses they want to provide, just like some schools only provides integrated courses and some provide modular etc. You have to ask the specific ATO what courses they have.
And just to clarify. There CBIR is just a different route to an instrument rating. You will end up with the same rating in your license regardless of choosing IR or CBIR.
Just note that if you "only" have CBIR theory (i.e. not ATPL theory) you will be limited to non pressurised planes.