In both cases, the exchanges were informed by phone about the account closures. In OKCoin’s case, the decision only impacts deposits made from their China Construction Bank account. The bank branch changed its policy on working with bitcoin-related businesses, but did not do because of actions or policies from the People’s Bank of China. The exchange has other accounts, and said that no other services were impacted.
CHBTC’s situation appears to be similar, with the Bank of China Beijing’s Baijiazhuang branch strongly encouraging the exchange to close its account after learning the nature of their business. CHBTC also noted that they had received no similar requests from their other banking partners, and were already prepared for the possibility of a country-wide ban on bitcoin businesses in the banking system.
Other exchanges, such as Huobi and BTC China, have not reported any account closures.