Thanks for the guide!
I've tested this dongle in Australia as well with Telstra, Optus, and Vodafone. The Huawei 3372 from Optus (or Office Works) auto-detects the APN based on the SIM inserted, even though it's Optus branded here in Australia. I am yet to test it properly, but you can set your own APN on these dongles for customer specific APNs or specific ones that you need.
For now, it's my dongle of choice for my 315s.