As near as I can tell, you can apply to only one with the same email address. The best dodge is to use use a gmail.com address with a plus-address. If your usual gmail account is [email protected], you can try [email protected] and [email protected] and both of these will land in your [email protected] account, but I think there is still a problem when you reply to taleo.

You do need to reapply from a blank slate to each customer. Once I'm redirected to a Taleo site for applying, I immediately exit the job application and look elsewhere.