I'm wondering about these two different situations. I read that linking together your own sites on the same IP does not work (PR is not valued since sites on the same server). Is that correct? Also if someone is offering a package of links (say three different sites) but the three sites have the same IP address is the PR value decreased by the big G machine. Thanks.
Google will know that sites that link together that are on the same C class of IP's are prob owned by the same person. It's not to say that google will penalize you, or devalue these links...but as far as true "votes" they prob don't count....same as if you're getting links from 3 sites that are on the same IP (or same C class of the IP)...it will (my guess) count as 1 vote to you.
I have also read that google has the capability of doing a whois search automatically to determine who owns each domain, it is part of their alogorithm patent. It does not mean they actually check that, but they have the technology to do it.
even if they count now (which I highly doubt), they won't in the future - so its' best to spread your links wide and far
These days google checks relevancy as most weighted criteria to give value or not. If contents are relevant then you'll get value otherwise backlink from other ips would not serve any good.