Illegal advertising - get the details of the number on the poster.
Unregistered pets - maybe they have an 'if found please call ...' tag on the pet, but no pet registration.
People dumping stuff illegally - if you were dumping general household/office waste, you'd probably have letters or bills with your address on it already, but I can think of scenarios where they might only have your email address to go on.
Wiretaps (ie: obtaining content) do require a warrant, and in the state of Victoria, where this is, half of all such applications for warrants are rejected by the magistrate. Getting the name and address of the owner of a phone number is a humdrum law enforcement issue, and really councils should have that power. Getting the list of calls made or where emails have been sent is a more serious violation of privacy (instead of "who owns this?" it's "what do they do with it?"), and I imagine that there's simply a legal loophole there.
The article has an amazing lack of detail and follow-through.
Even then this should only be available for law enforcement, not local fucking councils!
How did we get into this mess?