Upload & Sell: On
Anything with IS is still being fully supported by Canon, and they will probably continue to do so for another several years.
It is the very first big white EF lenses without IS that Canon abandoned/orphaned a number of years ago: 200 f/1.8, 300 f/2.8, 400 f/2.8 (MkI and MkII), 500 f/4.5 and 600 f/4.
Aww, thank you Petkal, that was the answer I was looking for. As I remember reading about some telephotos not being supported...but did not remember exactaly which one's.
So would one assume, parts are not available, nor any third party techs/service centers capable of working on them.