Is it permissible to hold a Christian prayer service or Mass in a congregational mosque, and what is the evidence for that?

It is not permissible to allow Christians or other disbelievers to perform their prayers and rituals inside the mosque, because their prayers involve polytheism (shirk) and the worship of other than Allah, and this is one of the greatest abominations. For mosques are for Allah alone, and Allah has commanded that His name be mentioned therein, and that they be exclusively for Him. The Prophet, peace and blessings be upon him, purified the Kaaba from idols and prevented polytheists from circumambulating it.