What's been done here, is just add a wildcard match, and then the internal hostname/domain to that. (I hope this actually applies here... I'm sure it would.. only if you had users from 180 locations, this list would be HUGE). From there Exim will search for that name in /etc/email-addresses and then plunk in the replacement at transport time.
If you didnt get the full jest, I suggest you hit up the Exim mailint-list archives and search for header-rewriting. It's got a few really good ideas for what to do. It seemed to have been a popular question a few months ago.
cheers!
--
It is by caffeine alone I set my mind in motion,
It is by the beans of Java that thoughts acquire speed,
The hands acquire shaking, the shaking becomes a warning,
It is by caffeine alone I set my mind in motion.
