There seems to be 2 different types of UK > IRL adaptors on the market they're both very small white boxes with an RJ11 on a 4cm cable and BT socket.
I'd suspect that the cheaper ones just connect the 2 line cables to the correct pair on the BT socket ignoring the ring wiring.
The more sophisticated version with its own capacitor is prob. better able to cope with any standard RJ11 sockets carrying the line on the centre pair. It would work fine in the USA, Ireland, Spain or anywhere else.
Some of the circuitry in the Irish sockets is used for automatic line testing. Irish Alcatel and Ericsson exchanges seem to run a regular overnight test cycle presumably to ensure that the loop is intact / working. We had DIY wiring hooked up in the US style and at about 3am every night all the phones would ring once!
As for the dial tones etc. The Irish network didn't really follow the same development pattern as the UK and used different equipment manufacturers to BT. Many of the tones and codes would be more like France than the UK
Originally most of the automatic switching was based around Ericsson ARF crossbar, more like scandinavia/other parts of europe. in the UK it would have been stowger step-by-step & various british systems.
from 1981-1985 all of the older generation equipment was removed and rapidly replaced by one of two digital switches ; Alcatel E10 and Ericsson AXE, some of the local crossbar switches installed in the 1970s remained through the 1980's but were relatively sophisticated and "parented" by the nearest digital switch. By about 1990 they were all replaced. The trunk network was fully digital by the mid-80s though. At the time telecommunications investment was seen as absolutely vital to developing the economy.
You'll notice a lot of french features in the system.
Dial tone, progress tone (bebebebe) if the system is waiting for a call to switch (e.g. phoning a mobile / abroad)
minitel was even introduced in the 1980s although it flopped rather badly.
even the first generation cardphones were identical to some of the France Telecom ones.
Eircom's audio samples of network tones probably from an Alcatel E10 switch:
http://www.eircomlab.com/audio/narrowband.htm