Yes, but what triggers the release ? Is there a proc in news that sets the news item as released ? If there were, that would be the best place to put do_notifications.
But I don't think there is.
The "released" state is determined solely by the release_date. The release_date is queried and compared with the current date when the user visits the news page.
I think you will need to create a scheduled proc or something that does the notification. From what I remember and as you described, news are displayed using a query that uses release_date. I think the current implementation was simpler (reason for it just using a query) than actually changing the state of the news (as CMS package implemented it).