I am sorry, but the documents provided do not contain specific information on how close flags and stanchions can be to the leading edge while performing telecommunication construction. However, the documents do discuss safety measures for leading edge work and working around power lines that may be relevant.

For leading edge work, a controlled decking zone (CDZ) may be established where typical fall protection systems are infeasible [1]. If using a CDZ, control lines must be erected not less than 6 feet (1.8 m) nor more than 90 feet (27.4 m) from the leading edge [1]. These control lines should serve as a visible and tangible reminder to employees working in the CDZ [1].

When working around or near buried utility lines, including communication lines, it is crucial to be aware of all such lines in the project area and avoid them [2]. Always have local utility companies mark the location of their lines [2]. If working near overhead power lines, maintain a safe distance [3]. If unqualified personnel are working near overhead lines, maintain a minimum distance of 10 feet for voltages up to 50kV [4].