Hi,
The best way to go about this might be to use a geo imagery layer and put a symbol layer on top of it to represent the trucks.
You can find information here: http://help.infragistics.com/NetAdvantage/DV/2010.2/CLR4.0/?page=xamWebMap_Geo-Imagery_Integration.html
about how to configure the various geo imagery options of the xamMap.

Below is a small example that moves a truck dot around randomly on top of the geo-imagery.
You will notice the one unfriendly part of this sample is that the 2 map layers don't pan at the same rate when you are panning the map using a mouse drag.
I believe keeping these pans synchronized is something we are planning on adjusting soon.

This sample uses OpenStreetMaps, but the principle is that same for the other imagery sources:
The xaml:

        <igMap:XamMap x:Name="theMap" >
            <igMap:XamMap.MapTileSource >
                <igMap:OpenStreetMapTileSource/>
            </igMap:XamMap.MapTileSource>
            
            <igMap:XamMap.Layers>
                <igMap:MapLayer x:Name="trucks"/>
            </igMap:XamMap.Layers>
        </igMap:XamMap>

And the code behind:

public partial class MainPage : UserControl
    {
        DispatcherTimer _timer = new DispatcherTimer();
        TruckEmulator _emul = new TruckEmulator();

        public MainPage()
        {
            InitializeComponent();

            _timer.Interval = TimeSpan.FromSeconds(.5);
            _timer.Tick += Timer_Tick;
            _timer.Start();
            this.Loaded += new RoutedEventHandler(MainPage_Loaded);
        }

        void MainPage_Loaded(object sender, RoutedEventArgs e)
        {
            InitMapCoordinates();
        }

        void Timer_Tick(object sender, EventArgs e)
        {
            double x;
            double y;
            _emul.GetCurrentCoordinates(out x, out y);

            MapLayer truckLayer = theMap.Layers[0];
            if (truckLayer.WorldRect.IsEmpty)
            {
                truckLayer.WorldRect = theMap.WorldRect;
            }
            SymbolElement ele =
                truckLayer.Elements.OfType<SymbolElement>()
                .FirstOrDefault();

            if (ele == null)
            {
                ele = new SymbolElement();
                ele.SymbolSize = 5;
                ele.SymbolType = MapSymbolType.Bubble;
            }

            ele.SymbolOrigin = 
                theMap.MapProjection
                .ProjectToMap(new Point(x, y));

            if (!truckLayer.Elements.Contains(ele))
            {
                truckLayer.Elements.Add(ele);
            }
        }

        private void InitMapCoordinates()
        {
            // define world dimensions 
            Point worldTopLeft = new Point(-180, 90);
            Point worldBottomRight = new Point(180, -90);

            // Convert Geodetic to Cartesian coordinates
            Point winTopLeft = theMap.MapProjection.ProjectToMap(worldTopLeft);
            Point winBottomRight = theMap.MapProjection.ProjectToMap(worldBottomRight);
            // Create Rect structure the map control's WindowRect and WorldRect
            Rect 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)
            };
            theMap.IsAutoWorldRect = false;
            theMap.WindowZoomMaximum = 80;

            // Change the map control's WindowRect and WorldRect
            theMap.WindowRect = theMap.WorldRect = winRect;
        }
    }



    public class TruckEmulator
    {
        private double _currentLat = 40.29029630058813;
        private double _currentLong = -74.55051898956299;
        public void GetCurrentCoordinates(out double x, out double y)
        {
            RandomlyMove();
            x = _currentLong;
            y = _currentLat;
        }

        private Random _rand = new Random();

        private void RandomlyMove()
        {
            if (_rand.NextDouble() > .5)
            {
                _currentLat += _rand.NextDouble() * .001;
            }
            else
            {
                _currentLat -= _rand.NextDouble() * .001;
            }

            if (_rand.NextDouble() > .5)
            {
                _currentLong += _rand.NextDouble() * .001;
            }
            else
            {
                _currentLong -= _rand.NextDouble() * .001;
            }
        }
    }

Hope this helps!

-Graham