Not specific to Canon lenses, though some were obtained unintentially:
I bought a Pentax 50/1.7 to go with my (first) ME Super. I had bought the lens off a seller on eBay for a rather steep cost of AU$45; although it was detailed as being in particularly mint condition. As I lived nearby the seller I broke the golden rule of eBay policy and organised a local pick-up/cash exchange. After testing the lens and handing over my cash, the seller asked, "Would you be interested in any other lenses or film cameras? I have a couple of boxes that will be difficult to take with me." He was moving interstate a couple days later and needed to clear some stuff. I sorted through the box, finding plenty of goodies including, amongst others, every model Pentax M camera (including ME-F), two Spotmatics (one "F"), several Pentax 50s of various breeds, other K mount lenses, two Olympus OMs, a Canon AE-1 and FL 50/1.4, two Minoltas, Rokkor 50/1.4, Kowa rangefinder (mint), Tamron Adaptall, Sigma primes, some studio gear (basic lights, stands, reflectors, etc.) and more.
All up, around fifteen cameras and ten lenses.
He gave them to me for free.