Sorry for digressing from the hard, solid nucleus of the thread, but...
Well, this was before they knew these guys were Renegades being led by Lore. They thought they were still part of the Collective, but different. So somehow they'd already theorized that the Borg were from the Delta Quadrant before Descent.
Hmh? When viewing that graphic, they supposedly were at the terminus labeled "Delta" already, having just traveled in the conduits. So probably they had empirically found out that they indeed were in Delta. No need to theorize much.
Also, their very next jump only takes them 65 ly from their previous position, so that can't be a quadrant-hopping trip. So it doesn't matter much which of these jumps was depicted in the graphic - both must have had their far terminus in Delta!
Post-mission analysis should not point to any great likelihood of the Borg originating from Delta, or existing in Delta in any significant strength, though. After all, no Collective members were encountered there. But Lore's conduits were accessible to Starfleet (at least until they dissipated, and the heroes didn't think this imminent); after Picard returned, further missions might have been sent to Delta, and some might have found evidence of real Borg activity there.
It's just that we still must assume that the belief that there are Borg in Delta stemmed from offscreen evidence, true or false. And even after seven seasons of VOY, we can't really tell if there were more Borg in Delta than elsewhere. Those transwarp nodes certainly seemed to be all over the galaxy, and there might have been more of those Unimatrix One things than the Delta one, too.
As for the quarantine on any "Starfleeters" coming through the wormhole, I sort of doubt they would have bothered with such a thing. At first, they thought the blood screenings worked; when they found out they didn't, they also must have realized that nothing would. And then they found out that a bunch of Founders loose on Earth did very little damage (if any - the Antwerp bombing may have been Leyton's work, too), so Great Changeling Hunts would actually be time wasted...
Timo Saloniemi
