I've been putting together a complaint to send to Tiscali about one of their subscribers breaching their TOS on wikipedia (may not work but worth a try). The problem is that the person caused most of the trouble they did while logged in. Thus checkuser is required to get hold of the IPs. Releasing these IPs would require foundation permission. Tiscali would also likely need to be able to contact the foundation to confirm any claims. I believe this gives us three options.
I send Tiscali the email without IPs and with the foundation's contact information. This is likely to archive nothing since Tiscali would have to contact the foundation before starting an investigation
The foundation gives me the IPs. This would allow Tiscali to begin an investigation but they would probably still have to contact the foundation. This has the disadvantage that the foundation has to release the IPs to me (even though I already know the range and Tiscali IPs don't tell you much I can understand the foundation not wanting to do this).
The foundation co opts my email and sends it itself. This allows it to keep the IP data private and removes possible barriers. On the other hand this could result in more work for the foundation.
I assume this situation will arise in future thus I am trying to start a general discussion as well as seeking answers for this specific case.