IMO, there are surely cases where the change to the subdomain being part of a larger site had no affect, in fact it may help the site by providing deep links. I believe these would be cases where the sub wasn't a link scheme. What I don't think is good is the same site having more than 2 listings!
2 listings is more than enough the rest is just a waste. If your site can't navigate to all sub domain pages unless all are in the SERP then IMO, you will at some point have a big problem and it won't be 30 listings in the SERP it will be 2 and a bunch of orphaned pages. I wouldn't assume the status quo is necessarily what Google expects for sub domains getting into the listings. IMO, the 2 listing policy is one of it's aces in the hole over Yahoo! and M$ results.

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