How to glean which wallets were involved in a multisignature transaction?
a multisig tx (e.g. 2of3) has a redeem script, which is basically the hash of three bitcoin addresses. This hash is included in the bitcoin transaction. As per today's knowledge, this hash can only be reproduced, if you have the three initial adresses. If you don't have them, then you can't know, which adresses were initially involved. A hash is a one way. Easy to generate a hash, but extremly difficult (or even impossible) for today's computers, to revert back.