The term isolated ground should be changed to shielded ground. The idea is that the outside of metal conduit or cable armor acts as an antenna for radio stations, atmospheric noise, and so forth but the inside of the metal acts as a shield against those things. I one time had an instance of a public address system that was picking up WQMX-FM. The cable for one of the microphones and the oscillator that acted as the change of class bell was and end grounded high impedance circuit using what is essentially a coaxial cable. The radio signal was coming over the outside of the cable. This is the reason why a lot of computer cables have an inductance core around the outside of the cable.

You cannot do an isolated ground using romex or pvc conduit, at not unless you are using shielded variable frequency drive cables.

Also, in the process of doing amp checks to figure out which neutrals are shared in commercial lighting areas, I figured out that about 10% of the neutral current for electromagnetic fluorescent ballasts flows through the equipment grounding conductor rather than the neutral. This consists mainly of high frequency harmonics and noise that flows readily through the lamp to fixture capacitance. Remember that capacitive reactance goes down as frequency goes up.

Also, unshielded variable frequency drive circuits will capacitively couple a high frequency tingle voltage onto adjacent motor circuits. For an allegedly deenergized 480 volt motot circuit this registers as about 30 volts on a voltmeter that is around 10,000 Ohms per volt. This consists of the high frequency carrier signal plus harmonics that flow readily through insulation capacitance, particularly THWN/THHN. It also flows readily through skin capacitance and has a rather nasty bite.