It would not be beyond the relms of possibility Saints fan, that a poster on here, could be a Police man or a person with connections to police work and therefore have access to such footage.
So they could have viewed it but cannot openly say so.
Another angle could be that they work for security firms that monitor such equipment. If the poster is stating facts that they have seen the footage these would be the most obvious answers, but there are other options such as knowing people at the club in question , or someone from the club copying the tape and sending it out via mobile phones.
There could be a few reasons why the footage has been seen, I see no reason for a poster to say they have seen something they have not. Especially if they are a moderator, and would look rather silly to claim to have seen an event, which once it goes to court would prove to be false.