CABLE SHARES FIRM ON JAPAN SPECULATION Shares in Cable and Wireless Plc <CAWL.L> firmed in morning trading on market speculation that its participation in a joint telecommunications venture in Japan would not be curtailed, dealers said. The company's shares were quoted at 372p at 0915 GMT compared with 364p last night. The dealers said the speculation appeared to originate in Japan. Cable has said it is resisting attempts by the Federation of Economic Organisations to merge two Japan-based telecommunications firms, a move which would have cut Cable's stake from 20 pct in one to three pct in the merged unit. However, the dealers were uncertain exactly how the dispute over the shareholdings had been resolved. British prime minister MargaretThatcher said in parliament last week that she regarded Cable and Wireless's participation in the Japanese venture as a test case of how open the Japanese telecommunications market really was. A spokesman for Cable said he was unaware if the speculation had any foundation. Cable itself had issued no statement today on the issue.