In http://community.jboss.org/message/521813, David Loyd writes
"Hmm. I was very sure that I did have a document for this, but maybe I only dreamed it."
David is the Server logging APIs/services lead. JBoss 6.1.0 uses jboss-logging 3.0.0.GA src: http://anonsvn.jboss.org/repos/common/ which gives a hint at question 1.
We modify jboss-logging.xml directly to provide consistent logging for all apps on the server. You can find some depth on specific logging questions here: http://community.jboss.org/tags#/?tags=logging.
I looked at JBoss AS 7 briefly and it seems to use a completely different logging configuration strategy so no help there. hope that helps.