It really depends on who you view as being the true Catholic church.Those who have assumed power in the last century(Vatican II) or those who go by 1900 years of strict,unaltered Catholic teachings.
Gibson's chapel is not in union with the Catholic Church and Rome.
No Traditionalist Catholic church in the world is really in union with Rome,they havent been since Vatican II assumed power and made sweeping liberal changes.
It is by no means a fringe group either,Traditionalists number in the millions.There would be more,but most papist Catholics view learning Latin and fasting as a drag.The imitation of Christ hasnt been fashionable for a good 50 years now.