The Nikon D4 uses all 14 of its bits all the time except for those lost to digital white balance.
The Nikon D800E is at 14-bit device with all codes present except for those lost to digital white balance until the ISO knob gets to 3200. Then the gain of the analog amplifier stops increasing and the output of the ADC is shifted one bit to the left, giving thirteen bits of resolution. There is another one bit leftward shift and concomitant loss of resolution to 12 bits at ISO 6400.
The Sony RX-1 is never a 14-bit instrument. It starts at 13 bits at ISO 100, and loses another bit in two of the channels at ISO 6400.
The Sony NEX-7 starts out a 12-bit camera at ISO 100, is 11 bits at ISO 3200, and 10 bits at ISO 6400. The NEX-7 is specified as a 12-bit camera, but looks like a 14-bit camera to RawDigger.