public enum SceneLayerDataSourceType : System.Enum, System.IComparable, System.IConvertible, System.IFormattable  

//Must be called on the MCT
var dataSourceType = featSceneLayer?.GetDataSourceType() ?? 
                           SceneLayerDataSourceType.Unknown;
if (dataSourceType == SceneLayerDataSourceType.SLPK)
{
  //Uses SLPK - only cached attributes
}
else if (dataSourceType == SceneLayerDataSourceType.Service)
{
  //Hosted service - can have live attributes - check HasAssociatedFeatureService
}

//var pcsl = ...;
//At 2.x - ISceneLayerInfo slInfo = pcsl as ISceneLayerInfo;
//         SceneLayerDataSourceType dataSourceType = slInfo.GetDataSourceType();

SceneLayerDataSourceType dataSourceType = pcsl.GetDataSourceType();
if (dataSourceType == SceneLayerDataSourceType.Service)
{
  //TODO...
}
else if (dataSourceType == SceneLayerDataSourceType.SLPK)
{

}