First time I've seen this. Seems weird to think it's even possible, and that CS were not programmed to auto-annex if this happens.
So -
1. Singapore captures Arretium from Rome and sets it to be razed.
2. I capture Singapore.
3. Singapore sees nothing wrong with letting Arretium burn to the ground.
So -
1. Singapore captures Arretium from Rome and sets it to be razed.
2. I capture Singapore.
3. Singapore sees nothing wrong with letting Arretium burn to the ground.