Terrysgirl,
I'm currently on a career break myself from the public service and i'm working abraod right now. It's my understanding that an individual cannot take up another employment in Ireland while they are on a career break. This does not prevent you from working abroad. People have different reasons for taking a break, for example to start/raise a family, travelling, to go back to college etc. Some will take the career break option to keep their job "open" so if their plans don't work out, they still have a job to come back to.
I must admit that I don't know of anyone who has come back to work after they've taken a career break. I can only speak for myself and say, the longer you are away the more difficult it is to come back.
Best of luck for the future