A Wide Open Mobile Phone Market
Demand for cell phones in Russia is increasing, with number of users set to double this year to almost three million; analysts say figure could jump to six million by 2001 if economy continues to expand; foreign investors and telecommunications companies are responding to opportunity by investing hundreds of millions of dollars to develop Russian mobile phone services; in latest deal, Telecom Invest recently teamed up with Sweden's national telephone company, Telia, to build Russia's first national network; photos (M)