ManyToMany cascade not working in migration scenario

Hei everybody,

I have two databases (one is a SqlServer instance, the other is in a SqlCe file) and I'm implementing a very simple syncronization system between the two. What I want to accomplish is to have all the data in the SqlCe file match the ones in the SqlServer instance. The SqlCe file's data are readonly (no update/insert) and the SqlServer/SqlCe schemas are identical except for the fact that the SqlServer surrogate keys are defined as INT IDENTITY NOT NULL while the SqlCe's are INT NOT NULL (this is mapped in fluent as Id(x => x.Id) for the SqlServer instance and Id(x => x.Id).GeneratedBy.Assigned() for the SqlCe). These are two of the models:

public class Customer
{
    public virtual Int32 Id { get; set; }
    public virtual bool IsDeleted { get; set; }
    public virtual String Name { get; set; }
    public virtual IList<Truck> Trucks { get; set; }

    public Customer()
    {
        Trucks = new List<Truck>();
    }
}

public class Truck
{
    public virtual Int32 Id { get; set; }
    public virtual bool IsDeleted { get; set; }
    public virtual Int32 Capacity { get; set; }
}

and these are the mappings for the two models:

public class CustomerMap : ClassMap<Customer>
{
    public CustomerMap()
    {
        Id(x => x.Id);
        Map(x => x.IsDeleted);
        Map(x => x.Name);
        HasManyToMany(x => x.Trucks).Cascade.AllDeleteOrphan();
    }
}

public class TruckMap : ClassMap<Truck>
{
    public TruckMap()
    {
        Id(x => x.Id);
        Map(x => x.IsDeleted);
        Map(x => x.Capacity);
    }
}

When I generate the schemas for the two istances (SqlServer and SqlCe) everything's fine and i get 3 tables (Customer, Truck, TruckToCustomer) as expected, with TruckToCustomer being the join table and containing the two Int columns Customer_id and Truck_id. The only difference between the 2 database schemas is the fact that for the SqlServer instance the surrogate keys are identities while for the SqlCe instance there is no increment defined - as i want it to be.

What I'm trying to do is to load all the data in the customer table on the SqlServer instance and write it on the SqlCe customer table, along with all the trucks associated and the data in the join table. I'd like to do it in one step so that's the code i wrote:

using(var sqlServerSession = sqlServerFactory.OpenSession())
{
    using(var sqlServerTransaction = sqlServerSession.BeginTransaction())
    {
        using(var sqlCeSession = sqlCeFactory.OpenSession())
        {
            using(var sqlCeTransaction = sqlCeSession.BeginTransaction())
            {
                IList<Customer> customers = sqlServerSession.CreateCriteria<Customer>().List<Customer>();
                foreach (var customer in customers)
                {
                    sqlServerSession.Evict(customer);
                    sqlCeSession.SaveOrUpdate(customer);
                }
                sqlCeTransaction.Commit();
            }
        }
    }
}

I was expecting this to populate my table with data for customers, trucks and the join table but instead only the customers table gets populated. If i go and peek at the trucks collection with the debugger BEFORE the session.Evict() call then the trucks collection gets correctly unproxied and persisted in the SqlCe schema but still the join table remains empty.
Also: if i just create a new Customer, add some new Trucks to it and save it (without loading it from the SqlServer instance), as in :

using(var sqlCeSession = sqlCeFactory.OpenSession())
{  
    using(var sqlCeTransaction = sqlCeSession.BeginTransaction())
    {
    Customer newCustomer = new Customer();
    newCustomer.Trucks.Add(new Truck { Id = 1 });
    newCustomer.Trucks.Add(new Truck { Id = 2 });
    sqlCeSession.SaveOrUpdate(newCustomer);
    sqlCeTransaction.Commit();
    }
}

everything works fine, so i get a customer with id = 0 in the customer table, 2 trucks with id 1 and 2 in the trucks table and 2 records in the join table with ids (0,1) and (0,2).

I'd like to know what I'm doing wrong, I'm out of ideas :-(

Thanks in advance

Andrea