Hi Richard
As Ireland was part of the UK he was as likely to serve there as in England or Scotland. The only information available is a card index on microfilm in Kew. So you will have to use a researcher, and I would not expect much in the way of useful information. It may only record his Company and dates and not even where he was, and certainly not his 'duties', and no information at all about his family. However if he was one of the small number of RE officers involved in surveying it may say so. You could also try contacting the Ordnance Survey of Ireland in case they have information on the RE seconded to them.
Like the RA the motto of the RE is 'Everywhere' meaning there are small numbers of them where ever there are other troops. And we are not helped by the fact that army lists do not even list officer's Companies.
Here is a link on the London Gazette about him moving to Canada -
http://www.london-gazette.co.uk/issues/20467/pages/1324 - so if you think he was a surveyor, you could also try the Canadian equivalent of the OS, as well as checking passenger lists.
Have you found the marriage record? If he was C of E, marriages in Ireland were certified before it became universal in 1864. So a post on the Ireland board may help.
Ken