The BTN's pre-flop play here was very odd indeed. I can only guess that he was multi-tabling and not paying enough attention to what he was doing. After the flop, his play seems standard.
I'm not sure if it would have been considered collusion if you had berated the BTN after the hand was over, but it is usually best to just let bad players play badly.
It is possible to imagine a situation, though, where the BTN raises it way up pre-flop with any two cards to provide "protection" for the SS (his buddy). Arguably this could be regarded as collusive behaviour too. Pokerstars
had some problems trying to police the play in their DONs. At one point, they were able to establish that there was a group of Chinese citizens who were colluding in the DONs on a large scale. Eventually Pokerstars just stopped offering the DONs completely, although I'm not certain it was entirely because of collusion. They have replaced the DONs with Fifty50 SNGs where 5 of 10 players are paid based on the size of their finishing stack.