User blog comment:Arbington/New ME4 Teaser Pics, Possible Upcoming Reveal/@comment-1679409-20131114091848/@comment-9753034-20131114155458

The closest thing to a naked turian we've seen strongly implies that the collar is part of their physiology. More importantly, every single turian seen in the series (armored or not) has it, so there's no apparent reason to assume the contrary.