I don't think you can "out of the box".
You'll have to write your own publisher...and piggy back on "FailureUsers".
https://github.com/ccnet/CruiseControl.NET/blob/master/project/core/IIntegrationResult.cs
// Users who contributed modifications to a series of failing builds:
/// <summary>
/// Gets the failure users.
/// </summary>
/// <value></value>
/// <remarks></remarks>
ArrayList FailureUsers { get; } // This should really be a Set but sets are not available in .NET 1.1
Here is the tech-spec:
http://confluence.public.thoughtworks.org/display/CCNET/Custom+Builder+Plug-in
Here is an example of someone who wrote one....
http://krisselden.com/2007/01/29/adding-a-custom-cruisecontrolnet-publisher/