The piece of art, after giving it a second look, appears to be a giant candle with a tabernacle sandwiched in between. A friend of mine was told by one of the "higher ups" at the Cathedral that the brass tabernacle sandwiched in the middle is the original. That is certainly a falsehood. The fact that a collection of Catholics on a chat board must sit around and question what the thing is is proof of its odd, its abhorrent nature. I have seen churches in England, Ireland, Germany, Poland, Italy, Austria, and usually the question must not be asked, What the hell is it? My guess is that the marble was a former piece of the original marble altar, and someone in the spirit of "renovation" decided to sandwich a tabernacle in-between.
When I was in England, staring at the statue of Martin Luther King, Jr., on the façade of Westminster Abbey, I said to those about me, "Wow, look at that, there is a statue of a communist, a prostitute-beating, PhD-thesis-cheating, individual, right there on the face of Westminster Abbey."