From what I have read and seen, isolated ground systems cause more problems than they solve.
When I explain to a customer, I describe the grounding system as a big pond of voltage. If you throw a rock in a lake, you don't get much of a splash - if you throw a rock into a small bucket, you disturb the situation a great deal more. The theory with isolated ground was to get a separate pond for the delicate equipment. However, this "delicate" equipment tends to cause the most disturbances itself. So, it ends up disturbing its own small pond a lot. Or put another way, the bigger the ground system - the bigger the pond, the less you notice the crap. The manufacturers that don't want their equipment to be influenced by other equipment crap tend to have equipment that craps the most. So they pollute their pond worse than anybody else. Better to add more ground points, more copper, more paths - then the crap isn't noticeable and doesn't cause problems.
Okay, you are electrical - talking sine waves - if you put together a lot of disturbed sine waves, the composite should be better than any of the disturbed sine waves. Add in a couple of nice heating coils and some other loads and the loads smooth each other out a lot. What does the sine wave have to do with ground? A lot of disturbances get on the grounding system. The bigger your grounding system, the less this influence is percentage wise.
In practice, this holds true. In one case, I advised against an isolation transformer for a sound system. Sound equipment guy insisted on it. The whole system hummed. I suggested taking out the transformer and reconnecting. They did - hum disappeared.
I imagine you can use Google to find studies that support this. Generally, I have found that my experiential episode with the description of ponds generally convinces people. Though I will not recommend voiding a warranty.
