It is telling that it appears that Leland/Control spaced much of the Section 31 crews. Doesn't really seem like a Borg tactic. I still wonder if Gant or maybe even Tyler end up being compromised by Control, but we will see.
If the AI becomes the Borg, it would involve some serious corruption to it's program, possibly during the battle and/or trip to the past in one of those probes. Not to mention hundreds or thousands of years of "evolution" after that.