Presumably the ticket taker is picking up the same thing, although why a ticket taker would be able to read an Urbanian IFF transponder, I couldn't possibly say.
It doesn't need to read the IFF (although there's no reason why it shouldn't - perhaps clearly identifying onself is standard ethics of robot wars, perhaps MM equipped her scanners with data ripped from, say, 113th's shell), it can just perform a scan and use MetroMind's information resources. Consider that even Memorious (what was left of him, anyway) did not know who or what HORUS was - but MM knows.
Probably for the same reason everyone seems to have a open wifi and shared harddrives, allowing MetroMind to stun Horatio at will, "redeeming cycles". :)
There's absolutely no problem with wifi. I didn't provide an explanation on the first page because, honestly, I had too much stuff on my mind, but here goes:
1. Most robots are equipped with a wireless receiver. You can use the transmitter on them and they will react - this means they are listening to something
. Usually, they are just annoyed, but some of them - most notably my all-time favorite (for obvious reasons) secondary character Gimbal - use the wireless channel as the standard mode of communication.
2. The Metropass booth identified Horatio and assessed available resources, nothing more. The greeter robot
installed the backdoor, physically. Only after that MetroMind could wirelessly "redeem" cycles (rearrange resources to different processes).
3. Goliath was a war machine for Metropol when humans lived there, of course he was listening to wireless commands, oh exploitable. I forget who says it (Clarity? MMB?), but Metropolitan humans excluded robots from military decision-making. There's just no way anyone with that attitude is going to construct a giant cannibal robot with a potentially unstable AI and not provide means to shut it down (especially for virus quarantine - it could have been hijacked! Where is your bot now?
4. MetroMind is literally a distributed system. Every Metropolitan robot that has ever traded her a megacycle listens for her wireless commands. Again, oh exploitable, nothing surprising and nothing videogamey about it; this is how things actually work, IRL even. Look up cellphone network hacking.
5. THE MOTH IS A SPY! This is my favorite crazy theory. It really does make sense to use tiny energy-independent robots to scout the environs; it even makes sense, if you're pressed for resources, to have them simply fly around in a more or less spiral pattern, prioritizing recharge, and just ping their location from time to time. If you see bots flocking to a location at night, there must be artificial light and therefore some remnants of civilization. The moth appears at night immediately before Scraper, so everything fits!
(More seriously, though, the moths were most likely created by humans for purely decorative purposes, which means they probably listen to basic commands from just about anyone. Why would anyone build a robo-moth that can't
fly in pretty patterns?)
6. How come Thanatos can infect just about anyone? It sure looks like human-like AI is a single invention, and all AIs work on very similar principles (compare Horus's log and Memento's speech), and you can choose to disable certain features or impose specific hardcoded restrictions when making a robot. Scraper speaks in one-word sentences and is apparently incapable of complex thought; the bartender on the other hand is capable not only of caring for his customers but of devising plans to circumvent his restrictions. Why would you give human-like intelligence to a robotic arm? Because you can, that's why! The AI framework is just software that can be copied infinitely, it doesn't cost anything. So everyone except possibly Civitas-made bots is seriously running Windows.
(Never mind that Thanatos is actually a secret superweapon of Urbani, no one is supposed to know the principles on which it works; think virus scares of the early 90s and weaponized viruses of the 00s that target important infrastructure objects running on customized software).
7. Possible survivors of Thanatos:
- Gimbal, because of his Civitas-designed fractal-based logic, and because Civitas was miles ahead of other cities in wireless technology;
- 187th, because he proceeded to shoot up the Council Tower upon arrival and then attempt to pay reparations, so he never traded with MM;
- Primer, same reason;
- Leo, because he consciously avoided involvement in the cycle trade;
- Crispin and Clarity, due to being dead (it depends on Horatio's mental state whether he's capable of repairing them, though);
- EFL, what with him being Urbanian and a Leobuilt Humanist - MM couldn't have possibly got her proxies' pincers on him;
- Goliath, who was following humans' orders but has no immediate reason to obey the Voice of Metropol.
8. So what's up with Horatio?
It looks like he's immune, simple as that.