Ok, finally I have configured the suspend-on-lid-close action everywhere via acpid.
For minimal changes to existing system wide config files (i.e. less manual overhead for the next upgrade), I did it like this:
cd /etc/acpi
mkdir local
echo -e "#!/bin/sh\npm-suspend" > local/lid.sh.post
chmod u+x local/lid.sh.post
It is then automatically called by /etc/acpi/lid.sh (if no gnome/kde power-manager running). I used pm-suspend, because it is already used in /etc/acpi/sleep.sh.
Now I have to figure out how to enable Fn+F4 system wide ...
Edit: Well, it seems that Fn+F4 -> sleep (everywhere) should work out-of-the-box under Ubuntu, because the thinkpad-acpi module is loaded by default (when booting a thinkpad) and the default
/sys/devices/platform/thinkpad_acpi/hotkey_mask
masks the Fn+F4 event, s.t. an ACPI event should be generated. A default acpid should then call /etc/acpi/sleep.sh (which calls pm-suspend).
First tests of Fn+F4 did not work (i.e. did not trigger acpi events) - but some strange side-effect (e.g.
cat /sys/devices/platform/thinkpad_acpi/hotkey_mask
, toggling the thinklight via
echo on > /proc/acpi/ibm/light
or something like this) made it work now ...