It is up to the Modem manufacturer to develop their own drivers. The same
is true of 802.11. If you embedd 802.11 or modem functionality into the
device, then you would create the driver. however, if you use somebody
else's chip, they will likely provide that for you. If you are talking about
using the phone as a modem (i.e. connecting it to a laptop and using as a
wireless modem) then the OS does support basic modem AT commands.
