Just found this website (to see all listings use scroll bar on left) ....http://gis.icao.int/ff1/FindRegional_Country.php?back=Back®ion=EUR&FindCountry=IRL
Appears to have been updated in 2016 and from the frequencies I have heard in use looks accurate.
Frequency = sector/area, (status, if heard in use recently), coordinates listed
120.040 = U1+U2+U3+UEXT, (confirmed), N52 42 W008 55 (SNN airport)
122.980 = U4, (NOTA, confirmed, primary), N57 W15 (SUNOT waypoint)
125.875 = U4, (NOTA, confirmed), N52 42 W 006 20 (typo? - 100nm SW of SNN)
127.130 = U1+U2+U3+UEXT, (confirmed), SNN airport
129.665 = U1+U2+U3+U4+U5, (status?), SNN airport
131.150 = U3, (confirmed, primary), SNN airport
132.150 = U1+U2+U3, (confirmed, primary), SNN airport
133.360 = U1+U2+U3+U4+U5, (status?), SNN airport
134.260 = U1+U2+U3, (confirmed), SNN airport
134.630 = U1+U2+U3+UEXT, (status?), N54 W15 (DOGAL waypoint)
135.230 = U1+U2+U3+UEXT, (status?), SNN airport
135.600 = U1+U2+U3+UEXT, (SOTA, confirmed, primary), SNN airport
135.730 = U1+U2+U3+UEXT, (status?), N54 W15 (DOGAL waypoint)
135.985 = U1+U2+U3+U4+U5, (status?), SNN airport
136.255 = U1+U2+U3+UEXT, (confirmed, used as sub for 134.260), SNN airport
118.975 = L1, (spare?), SNN airport
119.075 = L1+L4, (north, confirmed), SNN airport, - however transmitter can be heard on the EIKN LiveATC feed (72nm north of SNN)
124.700 = L4, (south, confirmed), SNN airport
127.500 = L1, (south, confirmed), SNN airport
129.300 = L4, (spare?), SNN airport
124.175 = Oceanic (status?)
127.900 = Oceanic (status?)
131.825 = datalink ACARS
136.975 = datalink VDL
Trying to make sense of the "remarks" that appear to relate to sectors or areas, ie: "U4" corresponds with northern NOTA sectors and "U3" with 131.150 etc. Not sure what UEXT means ? Sector "U5" corresponds with 3 frequencies I've never heard used before ? Obviously the sector configuration and number of required frequencies varies quite a bit depending on traffic volume and location of the NAT tracks.
Still trying to confirm what transmitters are located in the Shannon area (that you are hearing the controller on), as far as I can tell it's only 131.150 and 132.150 high, and 124.700 low ? The coordinates given by the website don't seem to correspond to transmitter location as most are listed at the Shannon airport (clearly not the case) or some even co-located with navigation waypoints.
The Oceanic frequencies 124.175 and 127.900 were used in the past to assign HF frequencies and voice position reports at 15W, but this is now mostly done with CPDLC, although I have heard some HF frequencies being assigned by ATC on the regular frequencies. So not sure the status of these two anymore ?
Any additional information appreciated.