That depends on how it is attached to the building. The bases of the towers on Sears Tower, for example, are an actual part of that buildings structure and if there was no broadcasting tower on them, would very likely count as a valid spire.
![](http://www.som.com/resources/content/5/0/4/3/8/8/1/1/images/SearsTower2.jpg)
©Whoever it says in the photo (too blurry to read), posted at SOM
For the first few years they barely had any antennas. The taller masts weren't added until several years after it was completed.
![](http://img266.imageshack.us/img266/2862/searstowerskydeckbrochu.jpg)
©Sears Tower Skydeck brochure from the 1970s
If there were no antennas or masts attached to them, those white stubs would still be there, because they're part of the building's structure. What would you call that?
BTW, the diagram system allows you to order buildings by roof height, which will display Sears Tower ahead of Petronas Tower.
Even if we didn't count 1WTC's spire, it would be an antenna and the building would be listed higher that way.