Newbigen discovers Anya's treachery early on but..

does nothing about it before he gets kicked off the train for Moscow and subsequently killed. I'm talking about the scene where Leo receives instructions from the Brain to take out a Russian uniformed officer (I believe that's how it was phrased,from memory). He carts his telescopic rifle to the roof of a building, takes aim and who's in the crosshairs but Anya! He doesn't tell Harry nor does he seem to take precautions arou8nd Anya afterwards. Also subsequently when Anya receives orders to kill Harry but fails, why then does nobody else in Midwinter's organisation finsih the job? Harry is able to operate with impunity even in Texas. Any ideas people?