After testing the News Calendar sample control I found that you will need to make one more modification to it in order to use it with a provider other than the default one.
In the NewsCalendar.ascx.cs, you will need to replace
NewsManager manager = new NewsManager(NewsManager.DefaultContentProvider);
NewsManager manager = new NewsManager(newsList.ProviderName);
Previously, the News Calendar sample control only used the default provider to populate its calendar, and with this modification you will use the provider that you set to your NewsList control.
Hope this helps!
the Telerik team