I notice that seems to be common with many utilities. They'll have a higher voltage distribution line, and the older equipment for that voltage seems to all be on the lower voltage lines. CPS Energy, for example, has A LOT of 34.5kv distriubution but I've never seen any 34.5kv bowls anywhere on their system but they sure got them on their 12.47kv lines.

I've noticed similar things like that for Xcel as well-there's a number of old 13.8kV lines here with dual voltage transformers but will never likely see the day when the taps are changed for 19,920V.