The Secretary-General’s bulletin ST/SGB/2003/14 details the Secretariat-wide policy, it applies to all nursing mothers of infants under one year of age and is not linked to national staff status. It is one of the rather straightforward policies, though local conditions in terms of facilities (“pump-room”, cold storage, etc.) may vary outside HQ and Offices away from HQ (UNON, UNOV, UNOG) and Regional Commissions). So for those aspects on specific facilities, it will depend on the duty station, but all duty stations are encouraged to support the policy through respective facilities, within their means. Staff should speak with their local personnel office to mind out more about the facilities and arrangements made locally.
To clarify, it is not possible to combine the two breaks allowed daily to one longer break, the two breaks are for two separate “feedings,” not one very long one.