Hi Per,
looks like my previous reply disappeared, so once again: there are more possibilites, one is to use Alerts. I would suggest to start alert on event ContactStarted - you have to register the event in view cluster CRMV_IC_EVENT_REP (transaction SM34). In runtime, the event is triggered when Alerting call status is signalled from CCtr.
Then in rule evaluate CAD (Call Attached Data) attribute, where the queue number or ID should appear.
Regards,
Dawood.