possibly the inspection is happening phase wise - say GZB-HPU, HPU-GJL, GJL-MB (something like that). besides they may also be checking if the TSS is integrated properly with the line traction or not, the unwired turnouts properly managed or not, any loose hanging/sagging wires or not, are the wires at sufficient height or not, pantograph contacts proper or not to ensure no entangling happens and the list is endless..most comprehensive check may probably be at GMS bridge...one of the crucial points..