Because DALnet uses Chanserv which runs as a background service, +r is not applied to channels on DALnet which are registered. It did used to be, but isn't anymore. $chan will not pick up on +r on that network.
People have given you valid solutions for an alternative though, i.e. the on notice events responding to chanserv's messages when infoing a channel. Channel services are not integrally server related though which is why it's not as simple as you wish it to be.
Regards,
