Example: emailing email@example.com gets translated to firstname.lastname@example.org
i tested a bit. so this is works:
on magnesium, add to /etc/aliases (not /etc/exim4/aliases/foo), it is configured like this:
"# Use the system aliasfile /etc/aliases for system domains" and rt.wikimedia.org is a system domain
i temp. put my own email address there as an alias for the unused legal queue, then sent a mail to the RT queue from zirconium.
magnesium delivered it to polonium and i received it just fine. (i got a permission error that i cant create tickets in that queue, but that is not what we are testing :)
so we can just add aliases there to forward some queues over to email@example.com