I don't know about that specific modem, but my understanding is that most Mobile Broadband modems from Optus are unlocked.
However, they use firmware specific to the Optus network, so you might have trouble with other network SIMs even if it is unlocked.
My 4G back doesn't work.
Whenever NBN goes down, I lose internet connectivity.
I got this modem as a replacement for the old one, and have just connected to the existing NBN device. NBN works, but the backup 4g does not.
When I login to the modem, it shows me that 4G connection is dormant.