Good question, but I have no answer. The catechism does seem to hold out hope for those outside the Catholic church under certain circumstances.
“Outside the Church there is no salvation”
846 How are we to understand this affirmation, often repeated by the Church Fathers?335 Re-formulated positively, it means that all salvation comes from Christ the Head through the Church which is his Body:
Basing itself on Scripture and Tradition, the Council teaches that the Church, a pilgrim now on earth, is necessary for salvation: the one Christ is the mediator and the way of salvation; he is present to us in his body which is the Church. He himself explicitly asserted the necessity of faith and Baptism, and thereby affirmed at the same time the necessity of the Church which men enter through Baptism as through a door. Hence they could not be saved who, knowing that the Catholic Church was founded as necessary by God through Christ, would refuse either to enter it or to remain in it.336
847 This affirmation is not aimed at those who, through no fault of their own, do not know Christ and his Church:
Those who, through no fault of their own, do not know the Gospel of Christ or his Church, but who nevertheless seek God with a sincere heart, and, moved by grace, try in their actions to do his will as they know it through the dictates of their conscience - those too may achieve eternal salvation.337
848 "Although in ways known to himself God can lead those who, through no fault of their own, are ignorant of the Gospel, to that faith without which it is impossible to please him, the Church still has the obligation and also the sacred right to evangelize all men."338
There is enough information given in the Jehovah’s Witness organization itself, even if presented as a way of converting Catholics to become Jehovah’s Witnesses, to say that they are not wholly ignorant of the Gospel, but that’s different from “knowing that the Catholic Church was founded as necessary by God through Christ,” which, of course, JW’s deny, seeing that they believe the Roman Catholic church is a major part of the false religions they see as Babylon the Great.