CALEA does not apply to Google (except Google fiber and perhaps Google Voice). Google does have to comply with FBI requests for emails and stored data, but they do not have to comply with CALEA (which mandates technical standards for the wiretapping of the phone network and most internet networks). Google does NOT have to build real-time domestic spying tools for the government, though it is arguable whether the 702 program (which PRISM is part of) does.
The FBI would LOVE to extend CALEA to Facebook and Google, etc, but this has not happened yet.
That said, it is likely that the FBI's backbone spying network (DCSNET), which was built for CALEA, is being used for PRISM.
http://www.guardian.co.uk/world/interactive/2013/jun/06/veri...
Moreover the language it was written implies that the same order was made to the other providers, changing just the recipient.
(If you are on the network which blocks access to Guardian, http://www.guardian.co.uk/world/2013/jun/28/us-army-blocks-g... you're missing a lot! Visit some friends, surf from their computer.)
It's not clear at all that this is legal, especially given the Supreme Court's recent ruling in Jones, requiring warrants for GPS tracking of automobiles.
Aside from that I'd say it's a very clear, and it's sad that there seems to be a pervasive inference that these companies are something something beyond what our elected law makers have forced them to do. Why isn't more angst directed at the politicians responsible for this?
Search for 51.
And as for warrants, no they do not always need a warrant. They only need that if both parties in the communication are US citizens. If none of them are no warrant is needed at all and if just one party is US then they (according to the Wikipedia article on PRISM) can wiretap for up to a week without getting a warrant.
Google et al. have fully complied with this law. The FBI manages the government-end of the CALEA tapping capabilities. The NSA makes requests to the FBI, which passes them on to Google, which flips a switch and enables the tapping of user "xyzzy123". From then on, xyzzy123's stored data and new communications get sent to the FBI through the CALEA connection, which forwards them to the NSA. CALEA also requires the service provider to provide all sorts of metadata about the user.
This IS "direct access" to Google's servers. The denials about this have been carefully worded things that all access is supported by some sort of legal process, etc. The denials are non-denial denials. Yes, GOOGLE (et al.), not the NSA, flips the final switch which sends the data. But Google is required by law to do so, so....... And once the switch is flipped, all of the data is flowing automatically to the NSA.
I hope this is clear.