[LabourofLove]

The handhelds that the DigSafe folks use here DO indicate depth of buried utilities by showing line/wire resistance. The fellow I used most recently showed me how to operate and read the units (probably a slow day for him). I was thinking about purchasing one until I discovered how very expensive they are.

[Stonehenge]

They have the depth info here, too. But as you now know, it's a bit unreliable, and they are probably creating additional liability by giving you depth info. That's my guess as to why they don't do it here. "DigSafe" is probably the name your state calls your folks - in Michigan it's Miss Dig, Wisconsin it's Digger's Hotline - but now they're all lumped together, sort of, by the 811 nationwide service.