I don't think there's any easy way to do it unless you can upgrade the Acegi bundle, as spring is very fundamental bundle in the container, two different spring version co-exist may cause more problem.
Would be migrating to Spring-Security an option (AFAIK Spring-Security was started based on acegi-security some years ago)? As Freeman said, Spring is fundamental to JBoss Fuse 6.0 (as Apache Camel and other components use it at it's core). It comes with Spring 3.0.7 and Spring 3.1.3 and I would advise to stick to these versions as they are intensively tested with JBoss Fuse 6.0.
BTW, what is the exact dependency in your pom?