I covered this in an earlier answer here. Briefly, there was no general "organisation" of a truce; terms were agreed on locally by individual units and their opposite numbers. Much the same applies to the famous "football match" (of which there were at least four); these evolved out of small incidents and could not be considered organised matches in a normal sense. For a longer treatment of the football matches specifically, see my 2011 essay for Smithsonian, here.