Given the permit in question is only given to residents, it would be motor_vehicle:conditional=private @ (Mo-Fr 08:00-09:15,14:45-16:00).
However, given this doesn’t apply to ‘SS5’ permit-holders, this should also be added to the conditional restriction. How best to do that is… honestly something I’m not entirely sure of. I would do something like motor_vehicle:conditional=private @ (Mo-Fr 08:00-09:15,14:45-16:00); yes @ (zone=SS5). The zone key is used for residential parking restrictions; I don’t see why it wouldn’t be used for access restrictions in a similar manner. If not in the motor_vehicle:conditional=* tag then maybe just standalone as zone=SS5.