You could get around this issue (partially) by doing some broad prefiltering based on the HTTP_ACCEPT_LANGUAGE parameter. For example, 'en-au' goes straight through to the sponsor rather than being passed to trafficjuicer. This isn't really all that accurate, but the difference in real sales versus backup dialers could be worth it. Fixing it at trafficjuicer is probably a better idea.
Hmmm. I hope trafficjuicer doesn't assume that 202.x.x.x, 203.x.x.x, 210.x.x.x and 211.x.x.x IPs are all "Asia" and redirect based on that... those ranges include Australian and New Zealand networks too.