Aqueduct's health boost is applying to Wood Gathering Elephants, but the regen boost is not. Elephants acquire 720 total health with Aqueducts, boosted to 1080 with Loom. However the 3 health/second regen is not applied to them. Elephants benefit from everything else that benefit Villagers with Rome, including the movement speed milestone and all techs and advisors. I feel that Wood-Gathering Elephants not benefiting from Aqueduct's health regen is an oversight.