Wrong 7400 series. The TCM8 card is for just that, legacy Nortel Norstar TCM endpoints.
The 7400 series they're referring to are Nortel DECT cordless handsets that register to a digital mobility controller which connects to the IP office by way of TCM station ports.
An AT&T/Lucent 7400 series phone is a totally different animal, and they require 2 pair (4-wire) DCP ports which are not, and have never been available on any IP office hardware.