Hi Andy,
Thanks again for those suggestions – based on which we added tribe_events_before_list_widget and tribe_events_after_list_widget actions (in the context of the list widget of course) and you can see the code for those in TribeEventsListWidget::widget_output().
For some others we felt existing hooks were sufficient, such as tribe_before_get_template_part and tribe_after_get_template_part within tribe_get_template_part() for adding elements before or after the mini calendar widget, for instance (you can detect that the calendar widget is being used by accepting a $template parameter in your callbacks).
Does that clarify things?