Function apply_substation_points 

pub fn apply_substation_points(
    net: &mut BalancedNetwork,
    layer: &GeoLayer,
) -> GeoApplyReport

Join a layer’s substation points onto buses through the SubNum (or SubNumber) extras key: every bus in a matched substation takes the substation’s point, and the layer’s space becomes the network’s GeoMeta when anything matched. Replaced locations and a coordinate space change are reported in the notes rather than happening silently.