Referring this clause
"NFPA 850 126.96.36.199* Unless consideration of the factors in 188.8.131.52 indicates otherwise, it is recommended that any oil-insulated transformer containing 500 gal (1893 L) or more of oil be separated from adjacent structures by a 2-hour–rated firewall or by spatial separation in accordance with Table 184.108.40.206. Where a firewall is provided between structures and a transformer, it should extend vertically and horizontally as indicated in Figure 220.127.116.11."
Is this applicable also between Emergency Diesel Generator/equipment and Transformers?
Since as mention in the clause "between structures and a transformer" only.