Eircom uses low interleaving for Residential packages and the opposite for business packages. Here is a decent link that shows a little insight into the workings of eircom.
eircom i-stream ADSL
As to your ip's heres my results:
Pinging 84.244.144.63 with 32 bytes of data:
Reply from 84.244.144.63: bytes=32 time=23ms TTL=58
Reply from 84.244.144.63: bytes=32 time=23ms TTL=58
Reply from 84.244.144.63: bytes=32 time=23ms TTL=58
Reply from 84.244.144.63: bytes=32 time=25ms TTL=58
Ping statistics for 84.244.144.63:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 23ms, Maximum = 25ms, Average = 23ms
P:\>ping 81.3.59.170
Pinging 81.3.59.170 with 32 bytes of data:
Reply from 81.3.59.170: bytes=32 time=30ms TTL=50
Reply from 81.3.59.170: bytes=32 time=30ms TTL=50
Reply from 81.3.59.170: bytes=32 time=30ms TTL=50
Reply from 81.3.59.170: bytes=32 time=29ms TTL=50
Ping statistics for 81.3.59.170:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 29ms, Maximum = 30ms, Average = 29ms