gistfile1.txt

C:\Users\Will\dev\FactoryGirlSpike\InteropConsole\bin\Debug>ir
IronRuby 1.0.0.0 on .NET 4.0.30319.1
Copyright (c) Microsoft Corporation. All rights reserved.

>>> require 'factories.rb'
=> true
>>> u = Factory.build(:user)
=> CLR User: FirstName: John, LastName: Doe, Admin: False, Email somebody1@example.com
>>>

What about this:
[~] 1> ir
IronRuby 1.0.0.0 on .NET 4.0.30319.1
Copyright (c) Microsoft Corporation. All rights reserved.

>>> e = IronRuby.create_engine
=> Microsoft.Scripting.Hosting.ScriptEngine
>>> s = e.create_scope
=> Microsoft.Scripting.ScopeStorage

>>> e.execute("require 'factories.rb'",s)


>>> e.execute("u=Factory.build(:user)",s)


>>>