I've got the following mini script in '/etc/hotplug/usb/ct-includ-display' (plus an usermap):
echo "$PRODUCT $ACTION $DEVICE" >>/tmp/foo.log
case $PRODUCT in
07c0/1501/*) :;; # My device?
*) exit 0;; # no match? exit!
You see I've added some logging stuff at the top of the script. If the script is called from coldplug (reboot) $PRODCUT is set to the string '07c0'. If I replug the device $PRODUCT is set to '7c0' (without the missing zero). This was very confusing and of course inconsistent.
sys-apps/hotplug is useless with any recent udev version, and 2.4 kernels are no longer supported. Unmerge it and move on.
Thanks for the feedback. I've removed the packages from my system.