Sorry, I was looking at the wrong place. Now I got the code.
The core design wiki pages are somewhat out of date and need to be updated at some point.
Althought at this stage it is hard to say when that will occur.
If you have specific questions, please post them here and we will address them. As Tim said, the core/JMS facade went through successive refactoring waves, and we did not update the initial design documents, for efficiency reasons. Eventually, I will update them, but that task is not scheduled yet.