This is my honest opinion on this event. Take it as you will.
In my eyes this event is flawed for two reasons,
First reason being because Core are subjected to shoot both sides to stop each other from gaining the upper hand, as stated in the official event post.
Second, making it clear that both sides shouldn’t have been receiving help from non official allies, which means Order shouldn’t be helping Corsairs and Core shouldn’t be helping Outcasts that's the whole reason you have the Zoners pick a side.
However i will add this in, any faction that has the correct ZOI for this event should be able to intervene, for example Order can only show up to shoot both Core and Outcasts as thats Orders current enemies within their ZOI, if they got shot at by zoners for shooting the side they picked then so be it, this said for any other faction with the correct Zone of Influence.
Not specifying just causes chaos and the event goes sideways real fast, this also doesn’t exclude anyone because they have the ability to make an Indie character to join in on the event.