Bruno,
The JMS actions referred to above are probably the ones I wrote a while back and posted on the original MII Wiki (http://wiki.scn.sap.com/wiki/display/xMII/Manufacturing+Integration+and+Intelligence) in the "Customization" section: Customization - xMII - SCN Wiki
Here you will see in the section titled "xMII 12.0" the JMS actions and documentation on how they work.
For MII 12.2 I highly recommend using the standard JMS action provided with the product as they are using the standard NW libraries and yes you can support third party JMS libraries with this approach and here's the details:
Sam