Guys, sharing church buildings with Prots is part of the ecumenical movement championed by JPII. He personally lauded the directives for Ecumenism published by the Pontifical Council for Promoting Christian Unity. The rules on church sharing are laid out in those directives!! So this practice is FULLY approved by the Holy See beginning with JPII.
JPII in Ut Unum Sint:http://www.vatican.va/holy_father/john_paul_ii/encyclicals/documents/hf_jp-ii_enc_25051995_ut-unum-sint_en.html
By engaging in frank dialogue, Communities help one another to look at themselves together in the light of the Apostolic Tradition. This leads them to ask themselves whether they truly express in an adequate way all that the Holy Spirit has transmitted through the Apostles.24
With regard to the Catholic Church, I have frequently recalled these obligations and perspectives, as for example on the anniversary of the Baptism of Kievan Rus' 25
or in commemorating the eleven hundred years since the evangelizing activity of Saints Cyril and Methodius.26 More recently, the Directory for the Application of Principles and Norms on Ecumenism, issued with my approval by the Pontifical Council for Promoting Christian Unity, has applied them to the pastoral sphere.27
Directory for the Application of Principles and Norms on Ecumenismhttp://www.vatican.va/roman_curia/pontifical_councils/chrstuni/documents/rc_pc_chrstuni_doc_25031993_principles-and-norms-on-ecumenism_en.html
103. The term "sharing in spiritual activities and resources" covers such things as prayer offered in common, sharing in liturgical worship in the strict sense, as described below in n. 116, as well as common use of sacred places and of all necessary objects....
108. Where appropriate, Catholics should be encouraged, in accordance with the Church's norms, to join in prayer with Christians of other Churches and ecclesial Communities. Such prayers in common are certainly a very effective means of petitioning for the grace of unity, and they are a genuine expression of the ties which still bind Catholics to these other Christians.119 Shared prayer is in itself a way to spiritual reconciliation...
112 Although a church building is a place in which a community is normally accustomed to celebrating its own liturgy, the common services mentioned above may be celebrated in the church of one or other of the communities concerned, if that is acceptable to all the participants. Whatever place is used should be agreeable to all, be capable of being properly prepared and be conducive to devotion.
119. Regarding assistance at liturgical worship of this type, there should be a meticulous regard for the sensibilities of the clergy and people of all the Christian Communities concerned, as well as for local customs which may vary according to time, place, persons and circumstances. In a Catholic liturgical celebration, ministers of other Churches and ecclesial Communities may have the place and liturgical honors proper to their rank and their role, if this is judged desirable...
120. In the prudent judgment of the local Ordinary, the funeral rites of the Catholic Church may be granted to members of a non-Catholic Church or ecclesial Community, unless it is evidently contrary to their will and provided that their own minister is unavailable,123 and that the general provisions of Canon Law do not forbid it.124
139. When authorization for such ownership or use is given by the diocesan Bishop (sharing of buildings for worship), according to any norms which may be established by the Episcopal Conference or the Holy See, judicious consideration should be given to the reservation of the Blessed Sacrament, so that this question is resolved on the basis of a sound sacramental theology with the respect that is due, while also taking account of the sensitivities of those who will use the building, e.g., by constructing a separate room or chapel.