How can I customize the priority of change set delivery notifications?

Hi,

I am trying to build an RTC Extension with which I can customize notifications of change set delivery into streams that I am working with.

I know that it is fairly straightforward to customize notifiers through 'Window > Preferences > General > Notifications' by adding triggers for different priorities (e.g. alert for highest priority, red marker for high, yellow for medium, etc).

However, I have not yet understood how priority is assigned to "Deliver" events in the first place. Is the priority decided by the server or client? I was expecting the priority to be mentioned in the RSS Feed for change set deliveries but there is no such field there either. Anyway, I would like to set the priority of these events myself (through a plug-in) based on some custom criteria.

Could somebody please shed some light on the mechanism of assigning priorities to change set deliveries and how I could go about customizing them via an RTC extension?

Thanks,
Rohan

PS: I am currently working with RTC 3.0.1 but even if your answer pertains to a newer version (4.x) please do post it.