I`d say it`s safe to assume that Ba Sing Se has been fairly modernized. Maybe not to the extent of republic city, but I wouldn`t be surprised if we saw Technology such as radios and vehicles such as cars in the city
I think it would have different levels of tech for every ring.
Lower Ring - cabbage cars (they r cheap), some sort of auto rickshaw, maybe trolleys. Some radios but not that many, probably some faulty electricity as well.
Middle Ring - decent amount of Satomobiles, some cabbage cars, buses, trucks, and autorickshaws. All areas have electricity and streetlights.
Upper Ring - All luxury satomobiles, limos, but not that many roads (probably). Also there would be a lot of new tech because the rich live there
Like to see the monorail like a bullet train nice and stream lined.going around in two directions. two separate rails now. motorized. Maybe Upper ring like the UAE tall buildings. Middle ring like Berlin. Where the people play (malls, expensive stores) Lower ring like a common Midwestern town (usa) not many tall buildings but lots and lots of houses apartments. where the people live. Not to much cars. have a wonderful public transportation system.
I don't think ba sing se is that modernised. Yes, technology probably has improved but Ba sing se was very conventional and liked to stick to tradition. I do believe the rings still exist, but serve a different purpose. I don't think people are segregated and catergorised like in ATLA.
@Avatar Reiko nice point
I have a feeling that the Earth Queen is a teenager and Korra's age. I have a strong feeling that she is an EArthbender, since mike and Brayna said it would focus around Earth bending. What if Book 4 was titled 'Bloodlines' implying the FIre nation
Everything about what happened with Ba Sing Se years were already seen in books 3 and 4 of The Legend of Korra and more in the comics of Ruins of the Empire.