I can transmit on certain Amature/HAM frequencies, but only ones that my level of license designate.
This is just a comment on open air wave audio traffic. As long as the communication is broadcast over the open air whether on public frequencies or even business/private frequencies it's totally legal to listen in. It's one of the main reasons that a lot of public first response has moved to microwave closed system radios. it offers some voice encryption, and requires special setup equipment and authorization to access that network.
Hope this was helpful!