FWIW I couldn't immediately reproduce the problem in Quantal. First I added an "iface eth0:0" to /etc/network/interfaces and ifup'ped this and ifconfig did show both eth0 and eth0:0. Then I did "ip -4 addr add 10.0.0.67/24 dev eth0 brd + scope global label eth0:0" and once again ifconfig subsequently showed both eth0 and eth0:0.
FWIW I couldn't immediately reproduce the problem in Quantal. First I added an "iface eth0:0" to /etc/network/ interfaces and ifup'ped this and ifconfig did show both eth0 and eth0:0. Then I did "ip -4 addr add 10.0.0.67/24 dev eth0 brd + scope global label eth0:0" and once again ifconfig subsequently showed both eth0 and eth0:0.