Can you attach a 3/4" condensation drain to a utility sink on a 2" circuit vented drain? I'm specifically concerned with the code that says "all fixtures will attach individually and horizontally to the building drain".

Can you attach a 3/4" condensation drain to a utility sink on a 2" circuit vented drain? I'm specifically concerned with the code that says "all fixtures will attach individually and horizontally to the building drain".
First, a condensate drain is not a fixture, and second you are not allowed to drain anything but sewerage in a city sewer in my area.
Having said that I would remove the utility sink tail piece and replace it with a branch tail piece,(see image). You may then connect the condensate drain to the branch tailpiece where it will be trapped. Good luck, Tom