As an Australian electrician (Well, now an AU sparky living in Japan), when we would install aircons, they would always get a dedicated feed from the switch board and an isolator switch.
The work as shown in Dave's photos is completely non-compliant and wouldn't pass any inspection.
Exposed single insulation, junction box not fixed down, I can't see the rest of the wiring but all wiring needs to be clipped into place and supported unless the roof space is less then 500-600mm or so (Have to check the exact measurement).
Also, at 9 amps, I wonder if they did a maximum demand calculation before hooking it into the circuit? I doubt so... Inspectors love to ping on that detail.... It's a good way to get nuisance tripping at the best (Why does my power always go out when I dry my hair with the aircon turned on??) and a fire at worst.
I'd be pushing for a dedicated feed with a separate breaker, it's no fun when a future faulty aircon takes out power to half the house during the night.
Kudos for choosing Mitsubishi too, they along with Daikin do make nice machines (I have all Mitsubishi in my place).