Gateway use case

I like Jabber.  My friend uses BorgIM.  I can still send my friend a
message by sending a jabber message to a specially-constructed jabber
id.  This is transparent to me using my favorite jabber client.  I
believe it's also transparent at the API level.

Now suppose I send a SOAP envelope to my friend's jabber id.  My friend
receives it and executes the SOAP processing model on it.  The
ImmediateDestination will be my friend's BorgIM id, rendered as a jabber id.

    * How many instances of the one-way MEP are there?  Who are the
      senders and receivers?
    * What bindings are used, and how?