[brudgers]

Oil immersion is commonly used for transformers in power distribution systems. The cylindrical transformers on power poles are cylindrical for the same reasons beer cans are, it's a good shape for holding liquids.

In commercial buildings it is also not uncommon for transformers to be immersed in oil. But oil's flammability creates substantial fire hazard and modern building codes address this by limiting the density at which the oil in transformers can be distributed; specifying fire resistant separation; and other substantial hazard mitigations as the hazard increases.

Since the oil around servers burns just like the oil around transformers, there probably won't be any special exception for oil immersed servers in the building code any time soon. So I'd bet against large commodity data center installations...a state sponsored agency's data center might be another matter.