There's a phrase I picked up during my 0.0 alliance management days with ISS but failed to properly understand until ISS began to fail and crumble. "An alliance cannot be destroyed, only pushed to fall apart from the inside".

BoB survived against all odds and I'd bet even if they'd been forced back to empire they would have survived in a form. But that vulnerability from within is what you need to keep an eye on. And that doesn't just mean spies, it means handling what happens AFTER the spies do their damage. BoB now face the task of keeping their alliance together in one form or another after having lost essentially everything. The corps are in disarray and their POS no longer have soverignty or alliance shield settings. That means no cyno jammers to keep the POS relatively safe and titans logging in at POS will be bumped out of the shield.

But my point is that an alliance isn't just a name, it's a collection of corps that like working with each other and if those corps reform then the alliance is still there. BoB has been pushed hard from the inside and the next few days and weeks will show whether they fall apart from the inside or stay together and carry on.