Watching for registration with python

[colin.helliwell at ln-systems.com]

I've been having a look at the modem-watcher-python example, and would like
to do something similar - namely wait until the modem has registered on the
network and then grab the MCC/MNC.
Is there some sort of event I can hook for this (similar to what the example
does with ' object-added'), or do I just need to poll?
Thanks