Hi Brad,
Yes OZ, does stand for Australia. I live in regional OZ too.
Where I live there is a Tower with a Telstra Transmitter on it about 2kms away. The “Librem 5” has 3 bars to indicate 4G Signal strength; because “every man & his dog” are on 4G now, most of the time I get “1Bar” (sometimes 2); with this Transmission it is pretty fast (quite acceptable). I only researched with Duckduckgo for the Bands that Telstra use; & with pleasantness & begging with a support person, I got the 4G frequence that the Tower near my address uses (as not all Towers always use the same frequencies) (of course that was essential for guaranteed reception at home).
The only Modem at present to use in Australia, that is on offer is the EU version of the one you are asked to choose from, between the two different versions. That EU version of the Modem, supports nearly all Telstra’s Phone mobile frequencies (except for one I think). My Tower only transmits on one 4G frequency from Telstra, & that is near 2000 (there is a slight range in each one of the frequencies).
Voice Calls work well (watch you don’t flick the Kill switch for the Microphone to OFF, has to be done deliberately though). SMS works great! (but no MMS yet); & the Terminal works well with most things, except for Saving edited work done in 'nano", as there is at present no “Control Key” on the Keyboard, but “apt install”, “ifconfig”, & most of the other commands I’ve use are find; even “nano” (except you can’t save edits). The GUI “Text Editor” seems to work OK too, as with other stuff the “Librem 5” comes with by default. 
(very happy)