Interesting that your code has moved to ban it, whereas the super neutral is specifically made legal in the CEC. I've never seen one before though. Was it common to install a super neutral while it was still legal?
We have a similar exception.
215.4 Feeders with Common Neutral Conductor.
(A) Feeders with Common Neutral. Up to three sets of
3-wire feeders or two sets of 4-wire or 5-wire feeders shall
be permitted to utilize a common neutral.
(B) In Metal Raceway or Enclosure. Where installed in a
metal raceway or other metal enclosure, all conductors of
all feeders using a common neutral conductor shall be en-
closed within the same raceway or other enclosure as re-
quired in 300.20.
But this is only allowed for 'Feeders', Not 'Branch Circuits' which is typically what you'll see.