PRISM was a confusing program because neither the people reporting on it, or the tech companies impacted understood how it worked. The claim was the NSA had direct access in to providers networks, and the companies claimed they did not - the "logical" conclusion was an abuse of CALEA or similar access granted to FBI.

It was later discovered the NSA capability was the direct result of tapping fiber optic cables between international data centers, nothing to do with lawful intercept capabilities.

We never got the full picture on PRISM. We do know that at least a part of the program was a direct result of tapping fiber much of the program also went redacted. I've posted this before but during 2010 the main data center I had access to was closed one evening and the next morning we had a mobile server rack tied back to main routing gear via fiber which was in a mobile rack, blacked out and fully tamper taped. We knew a three letter agency was installing it and all floor access was revoked for that evening as well as being in the building. This was not off long haul fiber but was off of main routing infrastructure. I don't believe PRISM was purely fiber taps and that these programs had deeper hooks. Unfortunately I don't have any evidence beyond the assumption based on the facts I had been given and what I physically saw. I've used and installed a lot of long haul gear and have seen and installed many fiber taps in my day, this implementation was hardly passive in nature. But, that's just first hand knowledge of a random patron of the Internet.