Utility transformers are generally regulated in the US using the National Electrical Safety Code. Local code officials have no authority over electrical utility systems and would not be involved in specifying the protection of transformers with deluge sprinklers (or any other form of active fire protection).
Now if a utility wants to install a deluge system, and the jurisdiction has adopted a model fire code like the International Fire Code, then the utility is required to submit the shop drawings and hydraulic calculations to the fire code official for review and approval. Installation of a fire protection system, even if it is not required, necessitates a construction permit in IFC Section 105.8.