I've looked up the lyrics for Claudy Banks without seeing the reference to Troy's walls. However, it might be relevant that there are a number of places in Britain (don't know about Ireland) called Troy Town (for some reason), and there are also a number of turf mazes called Troy Towns. I'm not sure how much these groups overlap. A turf maze is cut in the grass and in a unicursal labyrinth (ie no choices, it winds in and then it winds out). It doesn't therefore have walls. So not much help there.