I have seen cases where the street numbers and terrace numbers continue along a road e.g. 1,2,3,4, TceX 5,6,7,8 (st cont) 9,10,11...and also where the terraces have their own numbers, e.g. 1,2,3,4, Tce Y 1,2,3,4,5,6 (st cont) 5,6,7. I will have a look though further Thom's directories and let you know what I find.
If I'm passing through Rathgar at the weekend, I'll have a quick look and see if any of the old Terrace names remain.
Shane