On OpenVIX I just looked in
/etc/network/if-pre-up.d and see this inside hwmac
if [ -f /etc/enigma2/hwmac ]; then
macadr=`cat /etc/enigma2/hwmac`
That then tells me another hwmac file in /etc/enigma2 with just mac in with chmod 755, restarted box and then mac was changed to the mac I chose to emulate my Stalker subs (with no clashes in network router macs), then restarted box
Thats all I did anyways, easy peasy.
Note - this was done on Octagon SF8008 and Mutant HD51 not the machine you are asking for and just what I did.