There is nothing logged in Jira right now, but I am not sure if it should be added at this point due to the notice in the Introduction section of the spec itself.
“Notice (2010-06-21): The XMPP Council  believes that the Message Archiving protocol is unduly complex and will likely request a thorough review and simplification of this specification before advancing it to Final.”
It looks like it is bound to change fairly drastically in the future, so it would probably be best to wait until that occurs. I wouldn’t be surprised if it becomes obsolete and is replaced with something different altogether.
I am willing to add a task for it, if someone wants to take it on, but I think with that warning, it would be folly to put it in the main project.