Actually was just informed that 1-phase supply at up to 10KV isn't too unsual in rural areas to make it usable over long distances. In areas that have no small industry type customers and in older systems 3-phase was considered unnecessary and extra cost. Most farms used 220 V single phase as do all normal individual domestic properties. Rural 3-phase is a relatively new concept especially in remote spots. It was more common to split the load over multiple 220V supplies all originating from the same xformer and phase but all going to different buildings from the pole overhead each rated between 65 and 100 amp max. So for example a heavy milking machine might have its own 65-100amp 220V supply seperate from the house / other farm equipment same with heating etc. avoided 380V but still provides the necessary power. Closer to towns and even villages you get full 3-phase supply. These are extended where supply is required to feed large farms and small industry. there are thousands of miles of single phase 10KV though.

Here's the typical ESB single house supply xformer mounted on a pole top near a house in a rural area.

[Linked Image from movetoireland.com]