First, we are not clear how the AppleShare PC Card is used in this situation since it is not needed for communication to the host.
We assume that the PS/2 is on the Token Ring that is attached to the front-end processor using a Token Ring Interface Coupler (TIC). MacDFT 1.1 running over the TokenTalk NB Card on the same Token Ring can communicate directly to the TIC/front-end processor without going through the PS/2.