Pro Sites Custom Registration Page

Hi All,

I'm attempting to redesign our pro-sites sign up flow but can't seem to find where you're calling the registration template. I can see that the template is in ProSites_Model_Registration but I can't find any hook or filter that will allow me to completely replace this with a custom template. Do you have any ideas?

I'm sure it always used to run off of wp-signup.php but with the new version of pro-sites it seems to have moved away from that. Any reason why?