This is currently accomplished by storing the request object as a session attribute. An example of how this would be useful is:
When using a B2BUA and getting a timeout on a PRACK there is no simple way to send a CANCEL to the UAC side of the B2BUA without searching through the message list for the outbound INVITE. Support for getOriginalRequest would simplify the coding of this.
There was some concern about memory consumption expressed when this idea was introduced that will need to be addressed.