This was done in-order to reach the international community without much problem, as most of the TYO members were born and bred there. People who worked earlier in those countries were not effective because they weren't familiar with their system. According to the documentary, Father S.J. Emmanuel, President of the Global Tamil Forum made 2 or 3 visits to Sri Lanka to meet with Castro and once he conducted classes at the Nathan base on how to deal with the diaspora from Vanni.
Father S.J. Emmanuel
Castro