iPhone 5 in U.S. and Australia

[jnpy!$4g3cwk]

Is there a model of GSM iPhone 5 that works for voice and 3G data in Australia, and, voice and 3G/LTE in the U.S.?

Specifically, would an unlocked iPhone A1428 [ UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 2, 4, 5, 17) ]

http://www.apple.com/iphone/specs.html

work on both AT&T and T-Mobile in the U.S. for voice and 3G/LTE, and, in Australia for voice and (at least) 3G data on either Telstra or Optus (likely not LTE I understand).

Is there an easy way to figure this out?

 

[Applejuiced]

Yes, you just gotta get an official unlocked iphone from Apple in the US.

Here's its specs:
•GSM model A1428*: UMTS/HSPA+/DC-HSDPA (850, 900, 1700/2100, 1900, 2100 MHz); GSM/EDGE (850, 900, 1800, 1900 MHz); LTE (Bands 2, 4, 5, 17)

 

[jnpy!$4g3cwk]

Yes, you just gotta get an official unlocked iphone from Apple in the US.

Here's its specs: GSM model A1428*

Any info on which Australian carrier would work best with this phone?

 

[Applejuiced]

Any info on which Australian carrier would work best with this phone?

I have no idea mate.
They all should work fine as long as they are GSM then the iphone 5 will connect to 3G and hspa+
Not sure about LTE though.
Go to their websites and see what bands/frequencies they use and if they are compatible with the ones posted above.