/sbin/kmodule should report the nvidia module, if it is present in /lib/modules/$(uname -r)/modules.pcimap
As a last resort, we could provide in start_udev: cp -a /etc/udev/devices/* /dev/
modules.pcimap is overridden by pcitable. pcitable contains (in probably all cases) X driver mappings for the card.
ok, updated http://people.redhat.com/~harald/udev.html