Website and Webpage Backlinks

[SEMBasics]

What is the connection between backlinks for a website as a whole and an individual webpage? For instance, let's imagine that there are two webpages which are basically the same in terms of being optimized for a particular keyword, except that one page is found on a website with a lot of backlinks and the other one is not. In other words, all things being equal, does a page on a well optimized site have a ranking over a page on a site which is not well optimized, even if there is no serious difference between the pages themselves (I hope I'm making myself clear here).

For instance, there are many pages on Yahoo which (according to the Google toolbar, for whatever that is worth) have a PR ranking of 0. Is that still considered a valuable link since it is on Yahoo?

Thanks,

Moshe

P.S. I know that there are many factors that go into the ranking of a page, I'm just trying to isolate the relationship between individual web pages and the websites that they are found on in terms of SEO.