Hook Into Pro Sites New Site Registration

Hello,

I'm looking for a way to run a little bit of my own code when Pro Sites goes through the new site registration method. What's the best way to do that?

I basically want to "listen" for this and in my code, say in my functions.php, I want to trigger my own function to run. I don't really want to update the pro-sites.php file since that will get overwritten when updates come in.

I haven't been able to figure out a nice way to do this and I've looked into PHP decorators and wrappers - but at least what I tried, my class has to be called, and then it would get passed to the Pro Sites class...not really what I want either.

Does anyone have any ideas that might help?