A recent study from ITDP surveys the growth of BRT around the world over the past decade.
Note that IDTP thinks of BRT as something that matches the performance of rail using buses. ITDP's BRT standard excludes many of the projects that the US Federal Transit Administration calls BRT, which amount to premium buses in mixed traffic with minimal speed and reliability features.*
China has created the largest quantity of true BRT systems, but of course in per capita terms it's Latin America that is building true BRT most intensively. Fast-developing middle-wealth countries like China, India, Mexico, and Brazil are the sweet spot for BRT because (a) car ownership is still moderate, (b) government power tends to be consolidated enough that decision making is easy, (c) there is simply not enough money to build massive rail transit systems, at least not quickly and at the necessary scale.
This news is also interesting in light of the forthcoming Rio de Janeiro conference on climate change, and the rumours that China may be ready to commit to reducing emissions, putting pressure on India to do the same. Latin America, where many countries of similar wealth already have relatively strong climate change policies, is the perfect site for this conversation.
The other interesting stat is how rapidly the BRT revolution has moved. Of all the true BRT in the world, 75% was built in the last decade, mostly in middle-income countries, and the pace shows no signs of abating.
Fortunately, those middle income countries amount to a big share of the world, which could mean a real impact on global transportation impacts over time.
* (I tend to agree with ITDP's concern that the overly weak use of the term BRT is making it hard to talk about the original point of the BRT idea, which was to mimic what rail rapid transit does in terms of speed, frequency, and reliability. This meaning is inherent in the "R" in BRT, which means "rapid".)