These are really nice for first posted animations, I must say. Keep up the work.
Also, ironically, I am working on trying to get a simplified version of cities into TG. What I've done currently is tried the OSM conversion route. I've used OpenStreet Map to export an area (of Seattle) and than piped that into OSM2World, which will allow and OBJ export.
Haven't gotten to far into testing but you may want to give it a look. The only immediate concern I have is you'll have to export sections from OSM, accurate plotting your coordinates of each tile, and then bring them all through OSM2World, and weld the parts together.
Update: well it seems these would be good "maybe" for very distance cities. It seems some buildings are not correctly evaluated and you get floating floors/towers. Lol