You'll find the landing page refers only to UK records, but the offer does, in fact, include all the Irish collection. Access to the records will be free until 23.59 GMT on 23 February 2014.
To view these records you will need to register for free with your name and email address. Ancestry will then send you a user name and password to access the records. After the free access period ends, you will only be able to view the records in the featured collections using an Ancestry.co.uk paid membership.