As far as I know - and I did some looking up - ownership of the CN Tower itself has only changed hands once - in 1995 when it passed from the CNR to Canada Lands Company prior to the CNR's privatization.
I believe the management and operation of a number of aspects of the CN Tower had been outsourced, initially by CNR and then possibly by Canada Lands - in particular the tower base components (admission booths, gift shop etc.), observation deck and restaurant - to various private operators over the years. The last change I am aware of, and which took place a while ago, was termination of the outsourced management contracts (at end of contract term?) with Canada Lands taking over direct management of the previously outsourced managed components.
Also, my understanding is that the transmitters at the top of the tower - the various FM Radio, Television and Paging services which are located at the top - have always been the responsibility of Canada Lands, and previously CNR - management and operation of these components was never outsourced.
Presumably, Canada Lands owns and operates the land and structures immediately surrounding the tower itself, and is thus directly responsible for what is currently / has been recently erected there.
So - one change of ownership of the tower itself, and possible multiple changes of manager / operator of the tourist attraction elements of the tower over the forty year history of the Tower, but now all consolidated under the stewardship of the Canada Lands Company.