Not sure on the CO Lines part, I don't see why the One-x Mobile Preferred would care when using VOIP mode...
The Avaya one-X Mobile Essential client for IP Office requires an Essential Edition system license.
The Avaya one-X Mobile Preferred client for IP Office has the following licensing requirements:
• Preferred Edition system license
• One Mobile Worker or Power User license per client
Guide also mentions:
IP500s on Releases 4.2 and later, support the Avaya one-X Mobile Essential client. IP Office
Releases 8.0 and later, support the Avaya one-X Mobile Preferred client. The system requires
trunks that support clearing supervision, which include the following:
• IP500 Universal PRI not on T1 robbed-bit or E1R2 channels set to Loop Start emulation
• IP500 BRI
• SIP RFC2833
And:
If you are using one-X Mobile Preferred on a Windows server, you must install
the following applications before performing the administration:
• Avaya one-X® Portal
• Voicemail Pro with the Web Voicemail component installed