DNS Issues - seeking help or insight

I am testing a site which uses media servers in 3 regions. They have implemented location aware DNS in order to route requests to the closest media server. When I use WebPageTest all requests are going to the main west coast server where the DNS provider is. Can it be that Third-party DNS providers like Google and OpenDNS break the CDN because location can be calculated from the DNS server and not the enduser? I ma just trying to determine what I can do to get WebPageTest to reflect the results. I believe the media servers are sharing some load as CPU has went down on the west coast server and picked up on the central and east servers once they were turned on. Any thoughts would be appreciated.

Possibly - depends on which test location you are using and if your DNS servers support EDNS which passes the subnet for the client along with the request: http://www.afasterinternet.com/ietfdraft.htm

If you look at the XML (not the rendered HTML) for the testers page: http://www.webpagetest.org/getTesters.php you can get the DNS servers that are configured for every one of the test locations.