Extension to Cell

Is anyone familiar with Avaya's extension-to-cell feature? And has anyone gotten this to work on with Thirdlane PBX? If so would you mind sharing?

If you aren't familiar with Avaya's extension-to-cell it is a feature that can be turned on/off on the Avaya phone with a button. The pbx will ring the extension and cellphone at the same time. If you pick the call up on your office phone the cell phone stops ringing and if you press the ext-2-cell button it will ring the cellphone but put the extension on hold w/o music. This way if you return to your desk you can press the ext-2-cell to retrieve the call and hang up your cell phone.

Thanks
Dave