I found a pretty neat post (which I neglected to save, apparently), which talks about enabling the GPS functionality (that I didn't even know it had) on my "Telstra 4G Mifi" which is a Telstra-branded Sierra Wireless AC760S. It looks pretty easy - connect the thing via USB, install the USB tethering drivers, connect to the serial port for modem commands (mine was COM4), and issue the following:
AT!ENTERCND="A710" OK AT!CUSTOM="GPSENABLE",1 OK
(Note that the "OK"s are the device responding, there are only actually two commands to enter)
Reboot the device, and "GPS" appears in the configuration menu. I've not figured out if there's any use for it yet, but it's there.