During the trailer for the city, there is a glowing blue kiosk-like sign at one point that has the FF14 style alphabet used on it and some directional arrows. One person who translated it says the top one says "employment" and the bottom one says "soul delivery". That bottom one seems pretty significant in terms of a clue. The fact it also uses the regular Eorzian alphabet for that world also means that whoever lives in that technocity speaks the common tongue and uses common writing - they've shown alien or ancient civilizations before and those have usually used alien or ancient writing, so that suggests the city/civilization has been around for a while on the planet. Plus some ad billboards show regular looking humans on them.
Other things I've noticed:
1) If you look at the world map, there is this big glowy ass thing up in "North America" either in Canada or the Rocky Mountains area that has a name above it - it looks like the banner they use for major cities, so I assume that is Solution Nine. To the south of that is desert, so presumably that is going to be the American Southwest/Texas looking area we saw earlier. We know the desert area has trains and harvests cereulium like it is petroleum. JP fanfest also showed a train below a big glowing purple tower looking thing. So it stands to reason that the cereulium is being transported to Solution Nine and the place is basically run off magitek or something like magitek.
2) "Solus" is credited with inventing magitek and the Garleans ultimately reversed engineering Allagan tech to get a tech boost. And Allagans reverse engineered Omicron tech to get a tech boost. However, since we know who Solus actually was in reality, it would seem odd that some ultra hyperadvanced city would just be allowed to chill out in isolation - you'd figure it would be influenced and corrupted to try to hasten a calamity, much like Allag and Garlemond were manipulated. So either that never happened or the people running the city were savy enough to not buy that bullshit? They're going to need some really good writing to explain why American/Canadian Wakanda didn't have that happen to them.
3) Speaking of Wakanda, the glowy thing on the map looks like a meteor icon from raid fights sorta. Maybe Ultima or Omicron stuff crashed there long ago and the people there got a massive tech/power boost from it, kind of like how Wakanda got a tech boost from the vibranium meteor?
They mentioned the xpac will have two narrative arcs, so I presume it might be a bit like Stormblood in that regard. We'll have the Brazil area contest about the new leader, but the actual meat and potatoes part of the narrative bit will be all the shit going on in North America.