Colocation packages are not available for order online. They are handled manually, so if you need to signup please email your signup details, order will be verified as acceptable -- and then an Invoice will be generated which can then be paid online normally.
XO is a telco and offers transport (fibre) as well as transit (bandwidth) services across US. Their facilities are manned with onsite engineers.
But the Colo service we are offering is a Unmanaged service -- XO staff only helps out with remote hands, when needed, or if a server gets stuck on a reboot (fsck) . For other onsite config and network engineering, deployment there is an oncall engineer in the bay area itself.