Since the start of Season 2, Factions have been able to "breach" another Faction by firing TNT which explodes inside the core chunk and between the y-levels show in the /f raidinfo for that Faction. Further information can be seen on this guide: http://www.vaelox.com/threads/the-faction-core.1664/
While it was initially announced that Factions simply had to pass TNT through the core, this was scrapped before release and never introduced to the live server. The mechanic on the live server has always required an explosion inside the chunk.
I was under the impression that players were fully aware of this fact, as it was just how it has always been and is what is suggested on the guide. It is clear by the recent Ghosts vs Farside situation that this is not the case.
I will do my best to try and update any out-of-date information out there and will also be making sure that all staff are fully aware of recent changes so that players are not fed incorrect information.
As you know, we like to be transparent and post all changes made to the server at http://www.vaelox.com/patches/ - though this change wasn't mentioned as it never actually went live.
So yes, while Ghosts did manage to cannon their way into the centre of Farsides base, they never exploded any TNT inside of the actual core and therefore no breach was counted. I can understand the frustration, but I'm sure they can easily get into Farside again