I don't understand the last sentence. why Smith and Bell need to dependent on passers-by?
Until their elaborate staffs began to function they were marking time. America's multimillion-dollar communications empire had been reduced to a crude, truncated megaphone with two-thirds of the nation at the listening end and, at the shrunken mouth, two wire correspondents clutching commandeered hospital telephones. Smith and Bell shared the same desperate plight. They weren't learning much where they were. Yet should either surrender his outside line, the chances of finding another were negligible. They were dependent upon the cooperation of colleagues and tolerant passers-by who, hopefully, would be reliable.