Ancestry has uploaded a strange new database called Scotland and Northern Ireland Death Indexes, 1989–2013. I say strange because there's limited information about the source of the data – 'British Death Indexes. Various sources' is as much as the website will give away.
It provides transcribed death details for people who died in Scotland and Northern Ireland, including their name and title, town and postcode of last place of residence, date of birth or age at death, and date of death. The lack of GRO References suggests these entries did not come from official sources.
The entries showing Scottish towns as a last place of residence dramatically outnumber those recording Northern Ireland towns, even when searching for more obviously Irish names such as Doyle, Tierney and Murphy.
UPDATE: Ancestry provided me with source information after I contacted them. See blogpost.