This isn't a one-off type beat, and jumping to the conclusion that this will be a final conclusion to an event that prior to its cancelation roughly a year ago with Skorak's rage quit had been building up over the span of two years.
There will be more for us to chew on, relax.
Besides, even if the Rogues realistically saw the task force moving into the system via New York, as they reasonably would, the infrastructure in existence would give the task force advantage, and Philadelphia is just a lane down from Erie.
I know it's a game and people tend to lose sight of this, but a lot can happen in the span of a couple hours, and organizing a proper defense takes time, while everyone expects Liberty to make a move on Erie, and has been planning for it, Erie, and those groups avoided pre-emptively setting up a defense, since that would not only give Liberty an easy excuse, but keeping a standing force ready and properly supplied for long periods of time just /waiting/ for action isn't cost efficient, or even feasible for smaller groups, nevermind house spanning underworlders.
That leaves Erie a leg-down, but it was already a leg-down to begin with since Liberty owns the system to a good degree. So while there's going to be resistance, in a situation like this there's only so much it could do.