Ignoring security (usability)

Since some time, Deutsche Bahn rolled public wireless lan called "WLAN am Bahnhof" out at 25 railroad stations, you can choose between 4 providers. Sounds really nice, but beside the economical conditions, there is also at least one security issue.
Connecting to the network and opening your favorite browser redirects you to a encrypted portal. So far, so good ... the really bad news is, that the certificate expired over 6 years ago.

Broken certificate

This seems to be a normal behavior, since it happens often, that invalid certificates are used. This leeds to blunted users, which aren't verifying such certificates anymore, even when it's important.
Does anybody know a reasonable way to notify anybody who can solve the problem there beside the normal contact forms?