Create a PriorityClass with a very high value and preemptionPolicy PreemptLowerPriority.

Create a pod referencing that PriorityClass, with requests large enough that it only fits by evicting a running pod.

The scheduler preempts a lower-priority victim to make room.

This crosses namespaces, because priority is compared node-wide and the scheduler has no notion of which namespace owns the capacity.

The gain is scheduled capacity taken from another team, not credentials or API permissions.