Apply for private forum access from a different site

[NBSFlak]

I apply for a lot of betas, and what usually happens is companies have a registration form on their website. I sign up and get an email back with information about signing up for the private beta forums. They tell you to specifically use the email address that you signed up with for signing up with vBulletin. So I'm guessing I automatically get dumped into a user group when I sign up.

Does anyone know if there is a plugin that does that can do that or are these custom queries?

Thank you!