Hi. I'm sorry for the delay in answering your question - I didn't know until today that hubpages had this feature, and so I just discovered a number of questions that people have asked me!
To answer your question, the way that all ebay listings show up on google is through the feed that ebay sends them. Because auctions are so short (max. 10 days), most of the time they're buried at the "bottom" of the search resulsts. But store and fixed price listings have a better chance of showing up because they stay around a month or more. One strategy to add to your mix, if you haven't already done so, is to create a good eBay About Me page that describes what you sell and what your business is and includes a lot of key words, but without being spammy. About Me pages seem to be looked upon favorably by google because they stay around and therefore gain credibility with google's bots. And, of course, when people go to your about me page, they'll look at your listings if you're selling stuff they're interested in.