If the NID is part and parcel of the Network, that is, if the devise is owned and operated by the telco, on the network side of the network interface, I don't believe it is subject to registration under Part 68 of the FCC Rules and Regs. The "protector" that is part of many installations is not subject to Part 68 Registration.
The installation of the "protectors", (carbon block and/or current limiting devices) so far has never been subject to electrical inspection (whether connected to metallic or plastic water pipes), so once again, if the the NID is part of the network, it probably does not require to be approved under the NEC/CEC provisions. However, it would seem prudent to ensure that the darn thing does not put places on fire. If it can, no self respecting operating company will buy and install them. Hence, it is irrelevant whether you need 3rd party listing under the Electrical Code. You'll need to meet the requirements of the relevant standards to meet the expectations of your customers. Ciao, Vic
