It is broadcast, basically the torque "allowed" by ASR, or whatever is the min of torque demands.

The only info I have on the VAG CAN bus are posted in these two documents:
http://www.nefariousmotorsports.com/forum/index.php?topic=236
http://www.nefariousmotorsports.com/forum/index.php?topic=226

To give a short result summary for this thread, here is what can be revealed from
the bootrom of the 2nd CPU on ME7.1 of the S4, that Tony extracted:

The 2nd CPU is just a slave I/O extension unit for the main CPU, no higher sophisticated functions are
included in the slave CPU. Data is exchanged between the two CPUs via the SSC in packets of 96 words.
The main CPU can set many hardware registers of the slave (e.g. for port directions, capcom's,
pwm's, adc's, asc) via a configuration message.  Then data messages are exchanged to make use of the I/O
functionality in the slave CPU.
During normal operation, the main CPU reads the values of input ports, ADCs and CAPCOMs of the slave CPU
and sends output port values & PWM data via the message exchange on SSC each 10ms.

There are over 10 digital input signals, the two EGT sensors, many (>10) analogue signals,
and about 20 digital output signals connected to the slave CPU.
Also, the control interface of the knock control IC (most probably the CC195) is connected to the slave.
For the analog knock voltage signal I'm not shure wether it is connected directly to the main CPU or the slave.
And the slave CPU has sensor signal G79 connected to its ADC, the main CPU reads this value and compares against its own ADC value thereby performing ETC monitoring.