LCIO files can be read and converted into HepRep 2 data by installing either the LCIO plugin or the org.lcsim plugin.
The LCIO plugin is available in the Plugin Manager of JAS 3 under hep/linearcollider/lcio.
The org.lcsim is available in the Plugin Manager of JAS 3 under hep/linearcollider.
Once either is installed, LCIO files can be opened and browsed, just like HepRep XML files. If you install both JAS will ask you to choose the plugin to use when opening the files.