The Right to Use (RTU) form is a two page PDF file that one can print, complete, and sign. Those with access to Nortel's PIC site can download this file.
When selling a Nortel PBX you want to be able to provide a signed RTU form that the buyer can use to transfer the RTU into their business name. If you are the current holder of the RTU in Nortel's database than you just need to get ahold of the blank form, complete, sign, and include it with the system when sold. No need to contact Nortel.
Having a valid RTU with a system being sold ups the value greatly as without the RTU the buyer will not be able to upgrade the system or obtain support from Nortel.