IGN Map editors are paid by Waze to edit parts of the North America and World maps. They generally focus on areas where major content is missing, there was no base map import for that country, or significant problems are occurring with the map and no local editors are available.
In the past, IGN editors were more active in the map, but there were situations where some IGN editors were not knowledgeable about particular areas. Some non-IGN editors would argue their presence may have made the situation worse. In North America the presence of IGN editors in the map are much less common now. They tend to focus on the World map in newly added countries with few local editors.
When an automated map problem is reported and an editor marks it as "not identified", eventually Waze will consider sending IGN editors to that location to make changes to fix the problem. This is one reason why "not identified" is not recommended for automated map problems.