I don't know if it has been mentionned here.
Concerning this: http://www.iapso.org/pdf/Review2003.pdf where the Watchtower is mentionned as a costumer of the IAPSO service of the UN, I have written on a french's forum some text, i hope that Didier could sum-up and translate my thoughts.
Just an extract of http://webbuy.iapso.org/conditions/conditions.asp to try to explain the problem concerning the condition to buy something with IAPSO:
""2.1 You are only eligible to register and become an Authorised User to use this Website and request Services provided by IAPSO for the purposes of assisting the UN System, governments receiving aid, organizations co-operating with the UN System such as donor government aid organizations and non-governmental organizations (NGOs), as well as internationally recruited UN staff members and experts with tax-free import privileges."