I edited my post to take the c12 out of the example list, since it is more complicated.
But I think most people argue that the c12 is cathode biased since the bias voltage derives from the return current from the plate voltage through R10, so technically, changes in the tube current will feedback to the operating point.
The U47 uses the same kind of trick as the m49b for fixed bias. The cathode is tied into the heater circuit so the resistor between the cathode to ground is much much smaller than in a cathode biased mic (i.e. 30 ohms vs ~2200 ohms). The bias voltage in the U47 is derived more from the heater current creating a voltage drop than the plate current creating a voltage drop. Thus, changes in plate current won't feedback to change the tube operating point, compared to a cathode biased mic, since the heater current is constant and keeps things stable, ie 30/2200 less.
