Is this a bug or a feature? In existing installations the file is kept and apparently works, but on a fresh install on a machine with 3 NICs the file is empty and the assignment to eth* IMHO random. In addition, yast2 does not allow to reassign the interface names which makes network setup a bit cumbersome. Workaround is probably to manually obtain MAC address with ifconfig and add lines such as
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="01:23:45:67:89:ab", ATTR{dev_id}=="0x0", ATTR{
type}=="1", KERNEL=="eth*", NAME="eth1"
to /etc/udev/rules.d/70-persistent-net.rules which is only trivial when you can copy&paste it from other systems 