This may get caught up in the Dividing Fences Act.
I think there is a more fundamental question to be established first which is, as Kaindub noted, who is responsible for the lot-side of the gate, based on the by-law passed to allow the gate to be built?
If the by-law includes a clause that establishes the lot owner as being responsible, then that applies. If it doesn’t apportion responsibility to any party, then it defaults to the owners corporation.
If you then discover that there are different parties on either side of the gate, then the Dividing Fences Act may indeed apply.
By the way, it’s because of conflicts like these that strata law was changed to to establish that responsibility for changes to common property must be assigned to either the lot owner or default to the owners corp. This wasn’t to make the owners corp responsible for all changes, but to make the owners aware that if they didn’t make sure responsibility for repairs was passed to the lot owner, then it would revert back to them in the future.