I'm familiar with the SCADA part (I work as an EMS/SCADA devloper), but before my current role I was actually an operator and we used "red-line" drawings in conjunction with the SCADA system to troubleshoot down lines/relays/lockouts/etc. They were all digital for ease of use. On the transmission side of the house we didn't use GIS all that much, but the DOC folks used it as their primary source.