Think of Chez Trief, the proprietors of which invite customers into their dining room but not into their kitchen or storage spaces.
New guy in town: "I'm throwing a big party next month, money is no object, and I think you should cater. May I see your kitchens?"
Owner of Chez Trief: "Follow me. Would you also like to see our storage spaces?"
The militarily most important portions of Ceres - the "infrastructure," if you will - are not susceptible to this kind of reconnaissance,
Surface buildings, their connecting tubes, and their radiation are easily detectable from space. No secrets there.
I've got the impression that Tanglenet doesn't need large-scale infrastructure.
I would expect most good-sized human-occupied buildings (or major sections of building complexes) to have their own power and air supplies, with backup. (Not for defense, just intelligent engineering in a hostile environment.) Depending on the economics, they might usually get their power and/or air from larger centralized sources, but wouldn't depend on them for critical needs.
What sort of infrastructure subject to reconnaissance do you have in mind?
A real invasion would better have been conducted much more subtly, with people infiltrated in small numbers over a long period, none of them showing any sign of UW service, many seeking work in those parts of the Belter economy such that they are enabled to gain control of key operations when the UW made its move to take over.
Perhaps this infiltration has already taken place, and the light company pictured in this sequence is merely the equivalent of a ceremonial guard - the obvious iron fist - being deployed in advance of the UW bureaucrats entering Ceres Spaceport to proclaim their regime.
If a significant number of new people had arrived in the recent past, I'd expect widespread speculative gossip. So, I expect that the invasion force will be the four 'canaries', the soldiers we've already seen, and any more that arrive later (which could be quite a few).
Since the arc is titled "The Christmas War" and it's only a few days until Christmas, whatever happens should happen soon.