If I'm reading your mind correctly the answer is yes if by duct you mean wireway, cable trough, etc. Doesn't have to be three phase either, although that is what we use it for typically.
You are correct. "Segregated" and "non segregated" have very specific meanings when referring to MV bus duct. There is also a third type, "Isolated Bus Duct", where each phase conductor is in its own separate metal clad enclosure. For more details, please see http://www.electricity-today.com/et/issue0403/mediun_voltage_bus_duct.pdf.
__________________
Experience: The knowledge you gain just AFTER you needed it.