Yes transients and homeless people sometimes live under bridges because it provides a semi sense of privacy and shelter from the elements.
But The Monon High Bridge is not that type of bridge as it's not a solid, wide platform providing a "roof" to anyone underneath. I recall it stated it had snowed somewhat a day or two before Feb 13th. I can believe DN may have been involved but that he or anyone would for any reason randomly choose to live under there as opposed to an actual bridge, jmo becomes a stretch of imagination.