Yes, the two GigE ports on the standby sup are active and usable. Do a show port and you will see all four ports:
Port Name Status Vlan
1/1 Uplink PWA700HSW3 connected trunk full 1000 1000BaseSX
1/2 notconnect 1 full 1000 No Connector
2/1 Uplink PWA700HSW4 connected trunk full 1000 1000BaseSX
2/2 notconnect 1 full 1000 No Connector