I can't post the link because the page on the site where I found it keeps crashing my internet explorer for the past 2 days.

I can't comment on the best practices thing or what X5's have been equipped with in the past. All I can say is that it pisses me off that BMW NA cannot, or will not, put together at least a list of recommendations for things like tires. Talking to individual dealers is pure agony. Half the time they have no clue and the other half they are making up an answer. BMW has an official TSB with oil recommendations for it's engines (i.e. M engines get a very special grade of oil, etc.) why can't they do the same for tires and even more perplexing, why can BMW Canada do it and BMW NA cannot. The X5 forum is awesome in many ways but the most frustrating thing is that there doesn't seem to be any official representation on it from BMW NA or BMW AG and with that there is frequently no "definitive" answer, only opinions. Can you imagine how awesome it would be if there was! No more useless threads on what's the deal with the A/V connector on the rear center console of SOME X5's and how the pin-outs work for it, etc. We would have a final answer, it could be posted on the main page and that's it. This would apply to a huge number of topics and questions. It would take X5 World from 80% effective to 110% awesome.

Honestly even with the BMW CA winter tire recommendations I am a little surprised, because I have been lead to believe that narrower tires are optimal in snow and so the narrowest is the best (for any individual car that is). This would mean that 17" tires would be ideal for the X5. That seems to be supported with the fact that BMW only sells snow chains for the X5 (3.0 & 4.4) in 17" size and if you look at the ETK it only lists winter tires in 17" size (unfortunately those are so out of date that they are not even being produced anymore!).