"If your company has set up the proxy correctly you won't know anything is off because they'll have arranged to have the proxy's internal SSL certificate registered on your machine as a valid certificate."
Yes, this is basically textbook MITM for SSL. This is why the NSA can't do this at "your local ISP", because it requires access to your machine...
And your machine doesn't access your local ISP and vice-versa?
Not for its SSL certs, no.
If company does that, I'll sue them. Except, most probably it would be me setting up the system anyway.