I am the Scanner that went down there. So far I have entered sewers two times on my scanner. Both have been for the sole purpose of forward recon for the Protection-Teams that were escorting CWU Workshifts that contained vital personnel and/or equipment to restoring the CP-1 elevator. I don't know how exactly, but its generally pure bad luck to any party involved that the first time, my scanner saw a whole rebel group including 3 vorts (which caused a major sweep and/or fight), and the second time, I found two vorts who were there by chance and attempting to hide.
The most recent one being the second time I have entered resulted in the six-man PT being abruptly thrown into combat when my scanner took a picture of the two vorts in the room right next to them, which resulted in a TBC firefight.
As per the comments above, yes, we only enter the sewers when something important requires we do, such as CPs escorting CWU workshifts that seek to repair combine infrastructure. We do not enter frequently, nor are we meant to even enter at all under normal circumstances, and we definitely are not meant to enter sewers at random times and go "Oh, heres a random person I stumbled upon, marked anti-citizen or bol'd for 603!". Additionally, scanners are expendable, which eases the cause to send them into the sewers as they can be easily replaced.
I also agree with the manhack thing, but as far as I am aware, manhacks are broken and just fly to the roof or sky.