I have never heard that people get killed for such things. I know they do get fined though. I think whoever claims such must prove that it was TTP who did those things, it definitely is not their official policy whatsoever. We know that sometimes even the Afghan Taliban may make mistakes but the people are encouraged to complain to the judges/ameers etc so that issues can be resolved.
With regards to the killing of civilians, they claim in each of the video's I have seen, that they do not target civilians at all. However, due to the nature of combat, civilians may be killed. If you look at the classical works of fiqh, this is dealt with and in the video's, texts and references are given. Something relevant to this can be found in Shaykh Azzam's (ra) book here: http://www.kalamullah.com/Books/defence.pdf
See under 'Evidence for the General March', part 6 where the issue of Muslim shields is brought up.