[CCs]

It uses your gmail id. This "profile.google.com/<emailid>" is there before the Buzz time, long before Google+.

[jamesbritt]

Interesting.

Some data points:

I have a few gmail accounts. One is for james.g.britt, but profiles.google.com/jamesgbritt does not resolve to the g+ page for that email address.

I also have a g+ page for [e-mail] (via google apps)

profiles.google.com/neurogami takes me to the g+ page for that e-mail address.