ASIO, the Australian Federal Police and Australian Border Force (immigration) will become one like super-department of people with rather intrusive powers.
Someone does not understand the system in the U.K. then again I'm surprised Turnbull can spell his own name sometimes...
Home Office has a lot of power sure, but not really in a police sense, the Brits leave that to the police itself and agencies such as MI5 and a few other much less well known ones, small, compact and fast acting, always been the British way.
It is facile to say Australia has a better record than the UK, we are a tiny population on a very large island, the UK is completely the opposite, and only a few miles away from a very turbulent sub-continent.
I get on well with the feds, find ASIO a bit bizarre, Border force I've had no contact with at all.