You are correct that there is no actual evidence than anyone other than an imm or an Imperial shadow who was in the right place at the right time could produce that would show factually that there was some sort of in game or out of game communication showing this collusion. However, I will offer you the idea that this is the most likely scenario.

1. Thera is huge and you are looking for one guy. One guy! And Glik is either gathering preps or killing people or logging off. He doesn't do much else so you have to know he is on the move constantly. So Glik and another Imperial hit the giant and break in. Now YOU want everyone else to believe that the fort gank squad (with a mage) showed up at the village randomly? Like they checked everywhere else in Thera and then said "Hey! We did not check the Village to see if Glik is in the Village!" The idea is preposterous. The most likely scenario is that Glik and crew came to beat the bricks of Zah who immediately called one of the Fort assassins to help. Yanni showing up to help wasn't called for specifically by Zah. She was just part of the already formed Gank squad. So It goes thus:

Massive Giant: Holy shit Zah you're about to get some shower sex you don't want!
Zah: Hey Fort assassin wanna come get you some of this evil emperor and warrior before they take my black cherry?
FortAssassin: (over CB) The Empire raids the Village! Gank Squad Assemble!

I would make the exact same argument about Marideth showing up with a wanted Klitori at the Maran. You think Glik or the Empire thief didn't tell Marideth "Hey were gonna slap up on these fortressites for a while, wanna come catch the criminal?" You would somehow theorize that just because the communication between Empire and Marideth is not somewhere logged that it cannot be proven and so didn't happen? You are wearing your blinders and ignoring the preponderance of evidence and probability.

2. When was the last time the village took or held the Orb? Surely Amatias was hanging around the Maran because he was going to raid and take the orb since Yanni is a mage leader, the same way Zah (when he was Battle Leader) thought it would be good to take the scales all the time when Cerybis was the tribbie leader. Rather, the preponderance of evidence suggests Klitori saw the village assassin scouting, expected at least Glik (and wasn't surprised by Mari really) and called in reinforcements. What the hell else would he have been doing there? Battle isn't warring on Fortress even though they have a mage leader the same way Battle was warring on Tribunal when they DID have a mage leader. But I digress.

Let me finish this discussion by saying that yeah: Glik is being a douche by full looting. He is decked out and doesn't need your stuff. He just doesn't want YOU to have it. But let his douchebaggery cloud your judgement that there IS some kind of relationship between Battle and Fort that shouldn't be there. Battle should be warring on everyone. They are battle. Either get rid of the trash cabal or make them play it right. You don't attack Spire because the provost(Cery) is a mage then turn around and not attack Fort even though Yanni is a mage. You cannot have it both ways.