BTCChina
I think BTC-China always had fees until recently perhaps. What happened in Dec/19 is that they lost the deposit channel via bank transfer. They came up with a voucher system that apparently was not popular, while Huobi and OKCoin found a way to continue using banks for deposit. I don't know exactly what is the reason for their recent revival: they accept USD and HKD deposits, they have a mobile trading app, they may have eliminated the trading fees...
I´m almost 100% sure that they had no fees during the Nov/Dec bubble, maybe you could check out @JorgeStolfis posting history from that time, i´m pretty sure that he analyzed that, he´s a pro, but i´m too lazy to look by myself right now.

Edit: Found this:
http://www.coindesk.com/bitcoin-exchange-btc-china-eliminates-trading-fees/ from September 24, 2013
Bah, I won't bother, I don't trust @JorgeStolfi's brain.
I see that BTC-China eliminated fees in September 2013. Presumably by competition from Huobi and OKCoin, who had opened a couple of months earlier and did not charge fees from the start.
But the drastic loss of volume around Dec/19 coincided with the Deecember decree, and I recall that they were left without bank deposit channels while Huobi kept it open (using the CEO's personal account) and OKCoin soon restored theirs. I don't recall whether they restored fees on that date too.
At some point earlier this year, Bobby Lee was at odds with the other two CEOs on that matter: he wanted fees, they did not.