Нашел!
import zope.component
from zope.app.component import hooks
def AuthenticatedPrincipalCreated(event):
#print "Got event",event
principal = event.principal
print "got event",event,dir(event)
print "with principal",principal,dir(principal)
print "Context is",dir()
sm = zope.component.getSiteManager()
print "sm=",sm,dir(sm)
nearest_site = hooks.getSite()
sm2 = nearest_site.getSiteManager()
print "sm=sm2?",sm==sm2