Phone book is automatically created with the local users in the "end user" page. So if you need a new phone book entry, you need to add a new local user in cucm. And the phone book services are normally available per default for every hardphone.
You could create Local End User accounts with the needed information for these Emergency Numbers. You would configure the accounts with no password or PIN or Access Control Groups, so the accounts couldn't "do" anything. But they would show up in the Corporate Directory like any other End User.
