This unit file changes the OUI in the MAC addresses for enabled interfaces. It leaves the remaining bytes as is.
Copy [email protected] to /etc/systemd/system.
Enable it for each interface like this:
sudo systemctl enable oui@eth0
sudo systemctl enable oui@wlan0
Reboot then check your MAC addresses like this:
ifconfig | grep HWaddr
Tested with Raspbian Jessie (2016-09-23).
Most of the information I needed came from the Arch Wiki, but I had to play with the dependencies until it worked consistenly for both interfaces. (wlan0 would sometimes be broken after a reboot depending on the order in which the services ran.)