Current, there is no public API that let you know when the active view definition is changed. Expose an event for this.
Now, you can listen for changes in the active view definition by overriding the OnActiveViewDefinitionChanged method of RadScheduleView.
public class CustomScheduleView : RadScheduleView
{
protected override void OnActiveViewDefinitionChanged(ViewDefinitionBase oldValue, ViewDefinitionBase newValue)
{
base.OnActiveViewDefinitionChanged(oldValue, newValue);
}
}