June 20 (Reuters) - Britain's FTSE 100 index is seen opening 9 points higher on Tuesday, according to financial bookmakers. * BT: French telecoms company Orange could get 900 million pounds ($1.15 billion) by reducing its stake in British rival BT Group from 4 percent to as little as 1.33 percent, it said on Monday. * SHELL: A consortium comprising France's Total and Royal Dutch Shell won the 15th shallow water oil and gas block put up for auction on Monday, the Mexican oil reg