I went to get a cheap backup phone the other day, I think it was a Nokia 105 or something similar sounding. The woman at fortress told me it would not work with a Hk sim because it's a 2g phone and all the local sims, even prepaids, are 3g and 4g.
I'm pretty sure she's wrong but I don't know much about this stuff and there were no other staff present at the time to ask about this.