Yes, stole. As repeatedly evidenced - most recently with the Gemalto documents - the NSA far prefers to obtain keys surreptitiously than to go through the trouble of legally compelling corporations to provide them.
If said company would change the private key, obviously the same legal framework can be used to get this new key, in turn. So it's fruitless.
Of course, if it's an "inofficial" leak, a revocation and renewal of keys makes sense.