I don't believe we were discussing whether or not the so called "entity" as you put it exists. We were simply discussing the fact that all 3 were in the same building.Well, they're all talking to the same non-existent entity, so why not share a building, and share the cost of maintenance, heat, electricity, and so on.
Same with our military chapel in Germany. Never any problems. Just because you are of a different religion doesn't mean you have to hate each other. I was friends with one of the chaplains' wife. All the chaplains and their families and friends used to socialize together and there were many, many "a priest, a minister and a rabbi go into a bar . . . ." jokes told quite good naturedly all the time.Reading further, it sounds like they'll be in different buildings very close to each other on the campus.
We had one chapel on our common defence base in Turkey, which was shared by all faiths. Each had their own cabinet at the front of the chapel that opened up to be an altar. The priest, minister and rabbi held services at their appointed times. Sometimes inter-faith services were held. Everybody got along.