I never served as a CO, but was at one point on the wts bethel speaking list.
We had great liberty with our 'service talks', however we were supposed to stick to our outlines for the sunday talks. this sometimes led to occassional confusion and our being counseled as a group. once they told us to develop more meaningful service talks, after one guys gave a talk about ancient coins during the time of christ.
i remember one guy went totally off about how demonized space movies were. this led to the elders sending letters to the wts for clarification after the entire congregation went crazy with questions about new light, etc.
anyway the point that i learned was that speakers sometimes get clear instructions, but if they are far enough up the food chain, they may get away with taking more and more liberties.