Hi,
I've got some news on this. When i move my extension to a different directory (/usr/local/freeswitch/conf/dialplan/sockets/) and add an include element at the very sample place where the default is included, things work just as expected. That is, my default.xml now include following:
<X-PRE-PROCESS cmd="include" data="sockets/*.xml"/>
<X-PRE-PROCESS cmd="include" data="default/*.xml"/>
Cheers,
Max.