I doubt Google is getting any useful analytics from their CDN. CDNs are optimized for static content, and in particular are hosted on domains that don't have cookies set (because cookies break caching). All Google would get is
* an IP,
* a referrer from the first page on your site that included the script (no subsequent pages, because now the client has jQuery cached).
All in all, a pretty poor source of information compared to AdWords, Google Analytics, G+, hundreds of millions of Android users, and running the world's most popular search engine. At most they could crunch some browser stats or jQuery usage stats, but they already get that and more from their own services + crawling the web.
And even if this tiny amount of info were somehow a boon to Google, so what? It doesn't hurt you as a site owner.
* an IP,
* a referrer from the first page on your site that included the script (no subsequent pages, because now the client has jQuery cached).
All in all, a pretty poor source of information compared to AdWords, Google Analytics, G+, hundreds of millions of Android users, and running the world's most popular search engine. At most they could crunch some browser stats or jQuery usage stats, but they already get that and more from their own services + crawling the web.
And even if this tiny amount of info were somehow a boon to Google, so what? It doesn't hurt you as a site owner.