The Social Media Policy referred to in the article is a local policy which applies to Civil Servants in the Department for Housing.
There is no central Civil Service wide Social Media Policy. I would, however, like to highlight the provision in the Civil Service Code of Standards and Behaviours which states that:
Civil servants in category (d) may not engage in public debate (e.g. letter writing to newspapers, contributions to television or radio programmes, etc.) on politics, except if required to do so as part of their official duties.
(https://www.sipo.ie/acts-and-codes/codes-of-conduct/civil-servants/Civil-Service-Code-of-Standards.pdf )
The Code forms part of the terms of employment of all civil servants who are expected to adhere to it at all times.
Additionally, I would also like to highlight Circular 19/2009 'Civil Servants and Political Activity' - paragraph 14 specifically states that:
Civil servants, other than those in the exempted categories in paragraph 13, must not speak in public on matters of local or national political controversy or express views on such matters in the media (including electronic media and the press) or in books, academic papers, articles or leaflets .
(https://www.gov.ie/en/circular/461b3f526a6446e5a6b15aa6d11d42a2/)