I found a slightly different workaround, which works fine with italian telecom.
To use it, copy the following script to a text file named, e.g., AppleChimi, then copy it to directory /etc/ppp/modems with the terminal command:
cp AppleChimi /etc/ppp/modems/AppleChimi
then open PPP Connect and choose AppleChimi.
# AppleChimi: X PPP workaround
#----------------------------------------------------------#
# Modem = "Apple Internal Modem 56k" #
# #
# Use AT commands to contact the Apple Internal #
# 56 K modem #
# #
# Version = 1.0 #
# Date = 04/14/2000 #
# #
# Author = #
#----------------------------------------------------------#
# define ABORT keywords
ABORT "ERROR"
ABORT "BUSY"
ABORT "NO CARRIER"
ABORT "NO DIALTONE"
# delay for 3 seconds
# gives time to the modem to power on
"" "\d\d\d"
# send init string
# Original versione
#"" "AT&FE0W1Q0V1X4&C1&K3S95=1&D3S7=75S0=0"
# Modified: ignore dial tone
"" "AT&FE0W1Q0V1X4&C1&K3S95=1&D3S7=75S0=0X1S6=4"
OK ""
# increase timeout for connection
TIMEOUT 75
# send dial command
"" "ATD \T"
CONNECT ""
# perform extra work if necessary
# like login/password sequence
# ...
# script is finished !