HONG KONG (AFX-ASIA) – UBS Warburg has upgraded its rating on Beijing Datang Power Generation Co Ltd (991.HK) to “buy” from “hold”, with a target price of HK$3.20/share, after raising its NAV estimate to 3.20 from 2.90, analyst Alice Hui said. (US$1=HK7.87). In a note to investors, Hui said the brokerage has a bullish view…