Crawling is only affected by the incoming links. Whether the incoming links are reciprocal or 3-way, it doesnt matter and the pages will be crawled when Yahoo Slurp follows the link.
You don't need triangular linking for Yahoo rankings, but Google it does wonders. Or you can even go quadriladeral linking and get some really intersting results.
Crawling a site has to do with 2 things: Links and URLs. If you have links to your site you'll get crawled. If you have SEO friendly URLs, you'll get crawled. 3-way linking can be very beneficial, if done correctly. But don't let that be your only source of links. Pay for some links. Do a press release. Write some articles and submit. Have an RSS feed and submit.