The http://repo.fusesource.com repository won't have geronimo-servlet OSGI'd jars. It only contains Fuse product suits and related sub projects. The "fuse-esb-18.104.22.168\system\" directory contains all necessary libraries for starting up Fuse ESB without needs to pull in jars from remote repositories. Therefore, you will probably find "fuse-esb-22.214.171.124\system\org\apache\geronimo\specs\geronimo-servlet_2.5_spec" jar only.
You might want to look at remote maven repositories listed in "fuse-esb-126.96.36.199\etc\org.ops4j.pax.url.mvn.cfg" file "org.ops4j.pax.url.mvn.repositories" variable in order to find all geronimo jars.