I use the 85 f/1.2L II in AI Servo mode on my 1D Mark IV and it works great for action and sports. The 50 1.2L not so much.The 85L does a bit better in servo for some reason, still I wouldn't use servo unless i had to. I no longer own the 85L but mine was version 1. I am craving an 85 again but would probably go to the sigma 85 F1.4 making it the first non-canon lens i'd own. Its just a proven lens and you can't deny it rocks, the build quality is no where near the 85L though. Still i wouldn't use it in rain or bad conditions anyway, just portraits and PJ.
I'd be insane to argue with that. No, the 85L was not my first choice believe me, for sports. For some reason, when I grabbed my camera bag to go to the bball game, it was already mounted on my camera. Normally I'd choose the safer 85 f/1.8 for bbal!!
However, the images I got during that game with the 85L were just something extra special than the 85 f/1.8 was giving me as far as IQ. So I began experimenting and for some reason, if you track in AI Servo mode for a while, maybe give the focus a second or two, it hits everytime. Again though, I agree, much, much better for still and portrait shots. For instance I photographed a lady holding her baby for the first time in the hospital yesterday and used the 85L and even then it still took about one full second to focus lock, so in bball season I'll go back to the 85 f/1.8.
Btw, I shot entirely with the 50L and 85L and there is just something magical about the color rendition with those lenses that you do not see indoors with the 50 f/1.4 and 85 f/1.8. Why 50 and 85? Boy that room was tight!!