With the audio input selector to MIC and the AudioMode set to 48Khz, I get stereo. I change the input CH1 switch to LINE. But, with the input switch(es) set to LINE, the firewire output changes to MONO (48Khz) captured by PPro. LINE 2 input has no effect. Now, I change the AudioMode to 32Khz and the LINE inputs deliver LINE1/LINE2 stereo to the Firewire ouput to PremierPro. Amazing!
They write a special marker to define the 4 audio channels that are used. This marker is not recognised by Premiere. The cameras are out of production (Sony since abandoned its odd approach in these cameras), and Adobe has not made a Premiere change.
Bottom line, use Scenalyzer for 48K capture from these cameras.