There are concerns thousands of phones, medical devices, mobile phone boosters in cars, location devices in trucks and farm equipment may stop working.
Basically 300,000 devices will stop working Monday. And the owners of things like fall emergency panic buttons might not know they don't work until they're needed. Literally could cost lives.
Could also be fun for a lot of Melbourne's MyKi card readers, if they've not managed to swap them all out yet (I did read it wasn't completed yet as they'd not actually got the readers delivered)
What they should have done is added 3498 as a number to call, using the same emergency routes as 112 and 000. Then migrated 3498 to 4G only so users could call that and test if they could make 4G calls over the emergency line or not.
If there's some technical reason that they all had to be moved (like, you really can't test until 3G and older are turned off) then at least users can test post-cutoff by attempting to call 3498 instead of by spamming the real emergency lines. That's still pretty bad, but at least they'd find out right away without having to either 1) disrupt emergency services for a non emergency or 2) find out during an actual emergency that it doesn't work