Calls to those scripts are inserted in /etc/ppp/ip-up and /etc/ppp/ip-down when you visit the "default PPP parameters" dialog, found at the end of the users account menu (policies area). Each time you do a change in this dialog, pppdialin checks that the ip-up and ip-down scripts are ok.
Note that this added functionality is controlled by a modified /usr/lib/linuxconf/lib/ppplogin and as such is only available to "chat" users (as opposed to PPP accounts using PAP).
linuxconf --modulemain pppdialin --disconnect account
This is an easy way to kill a PPP connection for a given account without having to seach which pppd to terminate.
The paplogin script was not supporting the feature of pppdialin and has been enhanced. Still PAP connection can't use all the feature but at least, they can use the proper defaults set by the module. This includes: