That's another way to prop up the market I guess, after pretty much one-way traffic in the Hang Seng (and Chinese stocks) since the start of the year. There was a gap higher today with the open being 2.7% higher than yesterday's close but the index has trimmed gains to 1.2% now before the announcement, which comes during the lunch break. Overall, the Hang Seng is still down roughly 13% on the year though.
I reckon with China fearing that their liquidity pumps are moving to offshore and unconventional assets, they probably want to do something to bolster their options in retaining as much flows as possible.