We have tried to give the Email - Inbound Routing Rules a go, and have setup a single rule to update requests on the SR or IN reference.
Done some testing, but nothing seems to be actioned.
Expression is set to REGEX_MATCH(subject, '.*\b[a-zA-Z]{2}[0-9]{8}\b.*') for our typical subject line replies of "RE: ICT Service Desk - (Company Name) - New Call Logged, Reference IN00038936"