Joker, I don't think it's that easy to just plant surveillance on a section of tunnels that are locked away or in operation. First of all, what kind of cameras could you use? How expensive are they? Where would they fit? How would they connect to an outside signal? Should they be wired? Would there be interference? Would the battery last longer than 12 hours? How would you cover them up so nobody notices, how do you even gain access to a tunnel without notice? How do you set up a base of operations if you're only there temporarily?

As an end goal, this might sound appealing if the tunnels are still even being used, but I posit that we start off real slow.