This is really buggered.
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