Similar situation here: The PME system used in some houses is not employed on mobile homes, so it's always a 3-wire cable throughout (only one hot leg, remember).
When you say the main disconnect, do you mean the main at the site service panel or the main disconnect at each mobile home? In other words, is it 3-wire with combined N/G up to the post serving each home then separate N/G, or 4-wire right back to the site's service entrance?
