I'm working on a group of 84 low-end condos (for college students). Each condo has 3 phase service and a 7 lug meter socket. The local POCO doesn't even have a tariff for residential 3 phase. Odd huh? Nothing 3 phase in the condo's themselves and no 3 phase loads at house panels. (Maybe some 3 phase for sewage lift pumps?) Are we saving any wire by going 3 phase?

"Are we saving any wire by going 3 phase?" NO....

Now lemmie get this right, this has already been installed this way? Where did they get gear for that?

Normally this would be done as 3-phase 120/208 building main, and only single phase to each unit. Only in rare exceptions would one find 3-phase actually in a residence, for the most part it is a code violation in many places.