The code doesn't prohibit more than one voltage if all are under 600V, it just prohibits PV circuits, i.e. DC, from being mixed with anything else. So AC and RS-485 are fine in the same raceway as long as the wiring is all rated for the highest voltage. But your DC would have to be partitioned or run somewhere else. (Optimizer output circuits are a gray area.)
I'm not aware of any exceptions.
Why does the 690.31 handbook commentary directly contradict the text of the NEC? And I know this isn't commentary left over from the previous edition, because that particular commentary didn't exist in NEC 2011.
Text of NEC: "PV source circuits and PV output circuits shall not be contained in the same raceway [etc] as [...] other non-PV systems, or inverter output circuits, unless the conductors of different systems are separated by a partition."
Commentary text: "Conductors directly related to a specific PV system, such as those in DC and AC output power circuits, are permitted in the same raceway as PV source and output conductors, provided that they meet the requirements of 690.31(B)(1) thru (B)(4) and 300.3(C)"
Those requirements mentioned in the commentary indicate to identify and group, and 300.3(C) states that the voltage needs to be as large as the largest voltage system. But they do not directly indicate that you have to partition or build in separate wiring structures.
