Not a myth. Cities Service was bought out mid-construction and the building was capped and sold to Oneok. I don't think the actual height was 60 floors when construction started, I think it had already been lowered to 35-40 floors, I don't remember exactly, but I do remember it happening.
Now, could you really feasibly add the additional height on, I don't know.
I thought the Cities Service building was the one that sold to Occidental Petroleum to the south of OneOk.
Ooops, wait. Figured I'd double check that. According to someone who posted this on Wiki, you'd be correct. Read on:
http://en.wikipedia.org/wiki/110_West_7th_BuildingNever heard that Oneok started life as a replacement for the original Cities building. Interesting they thought they'd outgrown the 110 tower in a matter of 9 years after being built.