This is a bit different and I've not quite seen anything similar.
We are running Moodle 1.9.15 on a GoDaddy server. Since we are a University, we aren't really able to use Paypal for the processing of out payments, so we've contracted out with a company called Acteva which has handled other event registration payments before.
They've created a connector between their event registration payment system and our Moodle registration that is supposed to fill in the info we need directly into Moodle. However, Moodle isn't sending any registration info to the student (username/password) upon paying.
I know its vague, but are there settings to allow the system to send this info?