WCF data services custom basic authentication - wcf

Question

I have an WCF Data Service in .NET and I am consuming this service with datajs in Phonegap. I am trying to implement authentication as decribed here: http://goo.gl/0xQvC, and sending credentials with OData.read method. When I read credentials in the service with HttpContext.Current.Request.Headers["Authorization"], I found they are empty. What I am doing wrong?
Service Code:
[ServiceBehavior( IncludeExceptionDetailInFaults = true )]
public class TeyunaDataService : DataService< Meteora.TeyunaServices.Models.TeyunaContext >
{
public static void InitializeService(DataServiceConfiguration config)
{
config.SetEntitySetAccessRule("Clientes", EntitySetRights.AllRead );
config.SetEntitySetAccessRule("Transacciones", EntitySetRights.All);
config.DataServiceBehavior.MaxProtocolVersion = DataServiceProtocolVersion.V2;
config.UseVerboseErrors = true;
}
public TeyunaDataService()
{
this.ProcessingPipeline.ProcessingRequest += new EventHandler<DataServiceProcessingPipelineEventArgs>(OnRequest);
}
void OnRequest(object sender, DataServiceProcessingPipelineEventArgs e)
{
var auth = HttpContext.Current.Request.Headers["Authorization"]; //This is empty
}
}
}
Javascript Client code:
OData.read({ requestUri: url, user: "pruebausr", password: "passprb" },
function (data, request) {
// ... code to procesing data (It works fine)
}, function(err) {
$.mobile.hidePageLoadingMsg();
alert("Error al obtener clientes. " + err.message);
}
);
Service web.config here: https://gist.github.com/3746043
I am using:
WCF Data Services 5.
IIS Express.