public sealed class UtilityNetworkLayer : CompositeLayer, ArcGIS.Desktop.Core.IMetadataInfo, ILayerContainer, IMetadataSource, System.ComponentModel.INotifyPropertyChanged  

// This routine obtains a utility network from a FeatureLayer, SubtypeGroupLayer, or UtilityNetworkLayer
public static UtilityNetwork GetUtilityNetworkFromLayer(Layer layer)
{
  UtilityNetwork utilityNetwork = null;

  if (layer is UtilityNetworkLayer)
  {
    UtilityNetworkLayer utilityNetworkLayer = layer as UtilityNetworkLayer;
    utilityNetwork = utilityNetworkLayer.GetUtilityNetwork();
  }

  else if (layer is SubtypeGroupLayer)
  {
    CompositeLayer compositeLayer = layer as CompositeLayer;
    utilityNetwork = GetUtilityNetworkFromLayer(compositeLayer.Layers.First());
  }

  else if (layer is FeatureLayer)
  {
    FeatureLayer featureLayer = layer as FeatureLayer;
    using (FeatureClass featureClass = featureLayer.GetFeatureClass())
    {
      if (featureClass.IsControllerDatasetSupported())
      {
        IReadOnlyList<Dataset> controllerDatasets = new List<Dataset>();
        controllerDatasets = featureClass.GetControllerDatasets();
        foreach (Dataset controllerDataset in controllerDatasets)
        {
          if (controllerDataset is UtilityNetwork)
          {
            utilityNetwork = controllerDataset as UtilityNetwork;
          }
          else
          {
            controllerDataset.Dispose();
          }
        }
      }
    }
  }
  return utilityNetwork;
}