I may end up telling more than anyone wants to know.
Power was first installed in '91-'92, to Bay 1. As the shop expanded, it grew organically. Harry was an electrical engineer, so he knew what he could get away with. We were also rather poor at the time, so the electrical system was as cheap as could be done. When the station was built, it was fed with an underground wire.
I believe the Bay 4 extension wiring is all overhead, no conduit through the concrete.
When we started talking about the Bays 1-2-3 extension toward the road, we knew the drop point had to move to Bay 4, which meant distribution had to change. By this time Josh Recave was involved, our electrician. Before the extension was started, we dug a trench (in November) from the corner of Bay 3 over to the station/freight shed (when we encountered the wire) and put in I think 3 conduits - one for power, one for telephone, and one for the future. Then when we actually excavated for the extension, Josh ran more conduit to various wall locations, before the concrete got poured. Also around this time, Josh began working on rewiring the entire shop with conduit, although this hasn't yet been completed (because we keep needing Josh for other things).
I presume conduit was run during the time when Bay 2 and 3 in the older part of the structure were concreted, but I'm not sure about that.
When we bought the house, we now had two electrical bills (still do), so that must have been when the idea of the central distribution occurred. Once that started to gel, the trench was dug from Bay 4 to where the building is to the Percival House, along with conduits. The conduit was used for the phone system and now the computer network. The bathroom got electrical and water conduit underground from the house, but we didn't add a third conduit for anything, which might have been useful for phone (or internet/wifi), nor did outgoing conduit get put in (other than to the septic). The garage's electric comes from the bathroom, and conduit was put in when the ramp track was built.