The CBC 's piece on this subject includes this from party director, Christina Topp:

Guest lists for the events are vetted by the party to "determine if any individuals are registered lobbyists with active files associated with the relevant department and, if necessary, take steps so that the individual does not attend the event."
 
"Fundraising events are partisan functions where we do not discuss government business." Hence, anyone who wishes to discuss policy at a fundraiser is "immediately redirected to instead make an appointment with the relevant office."
 
The party "takes great care" to ensure that all communications about fundraising events clearly identify them as partisan affairs, going so far as to drop the government titles of ministers or parliamentary secretaries who are featured at them. "We do not make any connection between fundraising and official government business."