Is there a way to automap a ManyToMany collection on a subclass?

Hi, I have an abstract class Publishable that has a tags collection. A Review object inherits from the baseclass:
Publishable is set as IgnoreBase<Publishable>. I'm also using S#arp Architecture so Publishable and Tag inherits from S#arp's Entity

public abstract class Publishable : Entity, IPublishable
{
    public virtual IList<Tag> Tags { get; set; }
}

public class Tag : Entity
{
    public virtual string Name { get; set; }
    public virtual IList<Review> Reviews { get; set; }

    public Tag()
    {
        Reviews = new List<Review>();
    }
}

public class Review : Publishable
{
    public virtual string SomeField { get; set; }

    public Review()
    {
    }
}

When persisting a new Review, tags are not created (because tags collection are mapped to Publishable and not Reviews).

I can solve this by creating an override map for Review for the Tags collection. Is there an alternative way to this without creating an override map?