XIMB is run by a Christian management however as far as my knowledge goes, there is no Christian Quota for admissions at XIMB. It would be same as implementing Hindu Quota or Muslim Quota. India doesn't permit bias or favor on the basis of religion, only caste.
I do not think there is a quota facility available for the christian. In India, there is reservation and quota on the basis of caste and no colleges are providing quota on the basis of religion.
