there's something called confidentiality that would make that VERY VERY difficult. We could monitor the site to see who bid on what, but even that wouldnt make a solid case. I have access to roughly two dozen computers on a daily basis, roughly a hundred when school is in. I'd be surprised if they bid from the same computer very often.
Even if we DID get some solid evidence like that, we would have gotten it illegally and it would be thrown out in court. Which would make it even harder to get similar legit evidence brought up.