I don't really notice an increase of the rate of fire for turrets or firebase's like it says it does. I also noticed when you hack it gets increased range. Things might be firing to fast for me to notice but it looks the same to me.
The rate of fire bonus is only in effect while at lv 3 and is best shown on laser turrets i find if you want to test it for yourself. Also the range bonus can be seen if you go into a blitz and test 1 round without and the next with hack. Although it says range bonus only on lv 2 so im not actually sure of what lv 1 does if anything.