Transit maps are interesting because they're often controlled at the regional level, sometimes by petty town fiefdoms that don't want to share the data and play nicely with others. That's why, in most countries, it's rolling out city by city.
China was "easy" to add as an entire country because it's controlled by the government at the country level. Most other places it needs to be brokered, acquired, added, sanitized, aggregated, and rolled out at the city level
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