There are not hundreds of carriers. I believe the number is sixteen.
It is not the rate that they are switched at but how fast they actually
turn on and off. Think dV/dT.
The unfortunately vague article I found (Elektor Electronics, Dec. 2002)
said that the (sub)carrier spacing is 66.666 Hz, and that they use 64
QAM modulation. So there are somewhere around 160 subcarriers in a 10
kHz wide signal) and at 6 bits per baud the baud rate must be in the
20-40 Hz range. (As I understand it, the signal is around 40 kBPS).
(There's more tolerant form that uses 16-QAM).