(a) The SEC feed can be subscribed to by anyone.
(b) Whether the delay was 0 or 100 seconds, the computer consuming the feed will always be faster than a human.
(c) The details of the study are murky and unknown. In particular, the data collection aspect is suspect given it sounds like the researchers received third party data not directly collected by themselves. How were the timestamps handled? Were various caching issues properly accounted for? (The SEC website is served up via Akamai, for example).
Anyway, it's great a populist topic these days. Evil HFT always beating you to the punch, etc. But in reality, it doesn't matter because they are always faster than you. I suggest you read this post by well known finance/trading blogger Kid Dynamite: http://kiddynamitesworld.com/someone-will-always-have-the-da...