A better way to show users there is an outage is to create awn announcement to display on the portal page. Having regular users look through a long list of incidents including betty's broken mouse, Bill spilled coffee on his keyboard and Sue forgot her password isn't an efficient way to identify an outage.
That said, you could create a role which has read only access to the incident table and then ensure the people you want, possibly everyone, has that role via a group or groups. However, there may be licensing implications of this as typically only fulfillers can see the incidents of others. If you made only the short description field readable, then this may not require a fulfiller subscription. I would check with our account team to be sure.
-Jeff
