Staff are left to cope, and sitting in for in excess of the 2 hour max is common practice when staffing is below minimums on very busy days.
Does Ireland have a legal restriction on controllers hours and working practices ?? The UK has a relatively robust scheme and offers the ATCO the level of protection needed in terms of duty times, rostered hours, fatigue breaks, etc. It's called SRATCOH and can be found here in Appendix D if you want a look :
CAP670