The brief Canadian Press story is silent on who levied the fine.  It appears to have been the Conservative Party itself, as this June 8 CBC story suggests:

"A spokesman from the Conservative Party of Canada said no decision has yet been made on how to deal with the situation. 

"One option would be to a fine. Each candidate had to give the party a $50,000 compliance deposit by Jan. 1, which was refundable if the candidate followed the rules.

"The sums still haven't been returned and could be docked if campaigns were found to have engaged in bad behaviour during the race."