The definition of public office holder in the Lobbying Act is very broad. It includes members of the armed forces and members of the RCMP. So it's very much anyone who receives a pay cheque from Her Majesty--or maybe not entirely, but it's very broad.
I think the commissioner has said this act is targeted at dealing with the registration and the activities of lobbyists. So the public office holder definition is not, strictly speaking, to capture the public office holders per se. Rather it deals with who it is that lobbyists must register having had communication activity with.