That wouldn't work without the company being at least passively complicit. Links between datacenters are encrypted. If you want even basic PCI-DSS compliance then links between racks must be encrypted (and a rack that uses unencrypted links must be physically secured). And properly implemented TLS or equivalent (which is table stakes for a company that takes this stuff at all seriously) can't be broken by the NSA directly (and if it could be then everything would be hopeless). Thus the MUSCULAR programme where the NSA put their own equipment in Google's datacenters - that's really the only way you can do it.
Remember how the legal regime in the US works with National Security Letters. Companies can be, and are, required to install these backdoors and required to keep their existence, and the existence of the letter itself, secret. Of course Google, Apple, Facebook, every other company with a significant US presence is in receipt of one of those letters and has installed backdoors - the NSA aren't stupid, what else would those laws and their funding be for?