Burying a Jew in a gentile cemetery/Burying a gentile in a Jewish cemetery:
Although the Poskim make no specific mention against burying a Jew in a gentile cemetery, or against burying a gentile in a Jewish cemetery, nevertheless, it is included in the above law that one may not bury a Rasha near a Tzaddik. The old age customs dating back to the beginning of our history testify to the establishment of Jewish cemeteries and the particularness of not burying a gentile in a Jewish cemetery, or vice versa. We are thus very particular not to bury a Jew in a gentile cemetery, or vice versa, not to bury a gentile in a Jewish cemetery.
 See Sefer Umikarev Beyemin 22 for a general overview of this subject; Igros Moshe Y.D. 2/152; 3/157; Milamed Lehoil 2/127; Tuv Taam Vadaas 2/253
 Shulchan Aruch and Nosei Keilim, however see Ritva Gittin 61a that it is forbidden to bury a gentile near a Jew
 Ritva ibid