Air Canada in the past was known for not dumping on their 767's and had the fuel jettison system disabled or not installed on their entire '76 fleet. They also disabled the fuel jettison on some DC-9 10's and 30's as I recall.
Airbubba you are unusually well informed but, alas, not 100% accurate. The fuel dumping system on the 767's was not deactivated on all the fins, just a small number of them (if memory serves). I believe quite a few of the inherited fins from the merger had the dump systems disabled. It wasn't a situation I was pleased about but sometime around 2004 or so they began to reactivate the 767 fuel dump system.
I didn't fly the DC9-10 (a bit before my time) and although I flew the DC9-15 I can't remember whether that variant had a dump system or not, but I can definitely confirm that
all the DC9-32's had a serviceable fuel dump system.