Well I give it a try. Created a simple class with a method. Put a version on the server lib and one on the web archive lib. It is loading the version from the web archive always.
I'm using JBoss 4.2.0.GA. I've checked the docs and they mention a WAR classloader that if servlet 2.3 is enabled it loads first from the WEB archive than from the parent. How do I know if am I using this model?