[Speedskater]

While not what we would call common, many of the better studios do have isolation transformers. See page 21 of this Middle Atlantic paper.

"Integrating Electronic Equipment and Power into Rack Enclosures"
'Optimized Power Distribution and Grounding for Audio, Video and Electronic Systems'

http://www.middleatlantic.com/pdf/PowerPaper.pdf

 

[Speedskater]

In general, studio wiring systems try to hold separate the lighting circuits (even more-so the ones with dimmers or LED's/CFL's lights) from the audio AC power circuits all the way back to the main panel-board if possible.

 

[Speedskater]

Back to the isolation transformer in my post #8. The one in the drawing is a 240V input with dual 120V outputs. You really need to look at the white paper, not just one drawing.

The Middle Atlantic white papers with addendum are at:
http://www.middleatlantic.com/resources/whitepapers.htm

The:
"Integrating Electronic Equipment and Power into Rack Enclosures"
'Optimized Power Distribution and Grounding for Audio, Video and Electronic Systems'

white paper is at:
http://www.middleatlantic.com/pdf/PowerPaper.pdf