While there may well have been instruments with internal bells in some countries, I have never seen the arrangement in Ireland.
In general, as far as I understand it, the Post Office and it's various successors maintained both the instruments and the pole routes. There were some exceptions, including the South Wexford line where the railway company took the responsibility on itself. This line was the last substantial new build in Ireland opening in 1906.
In some cases pole routes and way leaves continued to be used for years after the associated railway line was closed - one example being Dundalk to Clones which was still in use in the 1970s by the post office. I think parts of the Valentia line (and doubtless other lines) are still used by Eir for telecom cables of one sort or another.
In more recent years other pole routes carried little more than block wires and as time went on reliability deteriorated to the extent that Irish Rail found it worthwhile to plough it's own cabling adjacent to the track. As far as I am aware maintenance of the instruments still remained the responsibility of the Telco.
Traditional ETS working is still maintained between Tipperary and Waterford West and between Killonan Junction and Roscrea. There are instruments in place between Roscrea and Ballybrophy although this section of line is usually operated under manual token regulations.