I can assure you that PCL does not use only hubs as alternates. I took a number of delays crunching numbers with the load controllers to ensure we got everyone on board that we could take. It was rare to not be able to take everyone, despite the gate agents pulling their hair out. Not once did I ever get called in... the block times were so padded you could pretty much always make it in A0. The ballast issue was a big debacle after I came over to big D, I'm assuming that's been resolved since I don't hear people screaming about it anymore.
Nothing makes me dig my heels into the ground more than a pushy gate agent trying to hit D0 at the expense of everyone around them.