In ArcGIS Online and Portal for ArcGIS Online there is an option to supply a Bing Map Key. This allows the creation of web maps that are based on Bing Maps. Once these maps are created and shared, they display in Cartegraph based on the user.
If the Bing Map Key is removed from ArcGIS or there is an issue loading these maps in Cartegraph, the already created and shared Bing maps display in Cartegraph as similar Esri maps. This is how they display in ArcGIS, as well.