The use of GIS in utilities is a fast growing one. AM/FM stands for Automated Mapping/Facilities Management and is a subset of GIS specifically for utilities management.

AM/FM/GIS Software
GIS software specifically targeted towards facility and utilities management.

Telvent Miner & Miner
One of the most well-known consulting firms specializing in the AM/FM/GIS field. For users of ESRI products they are known for creating the ArcFM  extension.