flowerdj,

As I mentioned in the support case you have opened, this support is coming in v11.1, planned for May release.

As an interim work-around, Engineering has provided the following:  

Please find attached the ESRI Tile source. To setup the XamMap, you can use the following code with the attached file if you want to use only the ESRI REST service, but if your goal is to overlay a shapefile or add MapElements (SurfaceElement, SymbolElement or PathElement) then you will need to wait for the 11.1 release:

<Grid x:Name="LayoutRoot" Background="White">

        <ig:XamMap Name="igMap" Loaded="igMap_Loaded" MapProjectionType="SphericalMercator">

            <ig:XamMap.MapTileSource>

                <local:ESRIMapTileSource />

            </ig:XamMap.MapTileSource>

        </ig:XamMap>

    </Grid>

public partial class MainPage : UserControl

    {

        public MainPage()

        {

            InitializeComponent();

        }

        private void InitMapCoordinates()

        {

            // define world dimensions

            var worldTopLeft = new Point(-180, 90);

            var worldBottomRight = new Point(180, -90);

            // Convert Geodetic to Cartesian coordinates

            var winTopLeft = this.igMap.MapProjection.ProjectToMap(worldTopLeft);

            var winBottomRight = this.igMap.MapProjection.ProjectToMap(worldBottomRight);

            // Create Rect structure the map control's WindowRect and WorldRect

            var winRect = new Rect()

            {

                X = Math.Min(winTopLeft.X, winBottomRight.X),

                Y = Math.Min(winTopLeft.Y, winBottomRight.Y),

                Width = Math.Abs(winTopLeft.X - winBottomRight.X),

                Height = Math.Abs(winTopLeft.Y - winBottomRight.Y)

            };

            this.igMap.IsAutoWorldRect = false;

            this.igMap.WindowZoomMaximum = 80;

            // Change the map control's WindowRect and WorldRect

            this.igMap.WindowRect = this.igMap.WorldRect = winRect;

        }

        private void igMap_Loaded(object sender, RoutedEventArgs e)

        {

            InitMapCoordinates();

        } 

    }

}

Thanks,