This is totally risk free arbitrage strategy corporates can, and must, engage in. Of course, when this starts getting done on a large scale as it indeed should, but has not so far happened, such negative yield spreads will automatically be arbitraged away.
This includes increasing the flexibility of the RMB against the US dollar, with the trading band being widened to ±2 per cent from early 2014 and, more recently, the adjustment last August to the methodology for calculating the daily RMB fixing rate to make it more market-determined.