Mike do you know if the two structures are sharing one sewer line and tap into the city owned main ? If each structure has its own water meter do you know if each structure has its own tap at city owned main or is it one tap with two meters and just a portion of the line is shared ? If you don't know then your city public works desk can tell you if there is a sewer tap card for each structures address ( as well as if there is a water tap card on file for each address ( I used to have a property that didn't have a sewer tap card on file because it was on a shared sewer line with the home to its north)