Well im pretty damn familiar with this band and thats not how they sound, even on the record. My guess is that the vocals were processed live, or possibly after, hence the obvious fakeness in the vocal tone. Ive heard the demos dude, they dont sound like this.
Well im not going to fish trhough the entire performance for individual words that are obviously being shifted too high or low. It should be fairly obvious to anyone whos worked with tuning software of any kind where the mistriggers are. The dead giveaway is when the program tries to tune S sounds. Also, like i said before, voices naturally get thinner or more wavering as the notes are held, its part of human expression. And thats where the autotune shows because you dont sing in tune as youre breathing or starting and stopping a particular word. And yet, autotune will try to tune these things, and it sounds fakey. Dont get me wrong i love tegan and sara, but its processed very obviously in these performances. Particularly on the word "head" int eh second video, and the way Saras voice sounds when she doest the low harmony in the first video.
Just listen to the low harmony and tell me that isnt very obviously processed with a tuning program of some kind, either live, or in post. You can hear the formant lock in and not let up no matter what her inflection is. Thats the giveaway of processed vocals.