The Droid 4 only supports a single LTE Band, 13.
Thats around 750MHz.

You can find bands in use in Australia here.
13 is not among them.
(Don't use the site to check for device compatibility directly, the supported bands are stored wrong for most devices)

Here in Germany LTE also does not work and the 3G antenna of my Droid 4 is a bit worse than the one of my N9, N900 and Nokia 808.