By Echo Wang and Atharva Singh (Reuters) - Shares of Legence, the Blackstone-backed engineering and maintenance services provider, rose as much as about 12% above their IPO price on Friday in volatile trading, following a busy week for new listings. The stock opened below its $28 offer price before rebounding to close at$30.50 in afternoon trading in New York, giving the company a market value of about $3.2 billion based on shares outstanding listed in earlier filings. The San Jose, California-based co ...