[Exim] .forward filters and added headers

Right now (Exim 4.30), it appears to be impossible to filter on headers
which are added by redirect routers.

This is a bit unfortunate if you use poor man's mailing lists, like:

virtual_lists:
driver = redirect
domains = +virtual_domains
condition = ${if match{$local_part}{^[^/~]+\$} {yes}{no}}
require_files = CONFDIR/virtual/$domain/lists/$local_part
data = :include: CONFDIR/virtual/$domain/lists/$local_part
headers_add = "List-Post: <mailto:$local_part@$domain>\nList-Id: <$local_part.$domain>\n"
headers_remove = Return-Receipt-To
errors_to = $local_part-owner@$domain

Users on the same box can't use ~/.forward to sort mail based on the
List-Id: header.

Is there a workaround, or is this enshrined in the architecture? Since
the header is added by a router, this case appears to be different from
similar problems in this domain, so I'm somewhat hopeful that something
can be done about it.