Then all you have to implement, as part of the IAP code, is some support for the modem to implement the autoanswer code to establish the modem connection.
Just to keep anyone from getting lost with homemade IAP code where none is needed:
"as part of the IAP code"
should be:
as part of your code where it detect the request for IAP

Of course, if you want the customer to push switches and hold down signals etc (as opposed to NotTouch) you will need to include it in a homemade IAP code.

Erik