Depends on when and where they're constructed. See the other post by the health worker on this thread.
All the stuff built in Texas in the last decade or so has elevated or roof generators.
I guess the older hospitals had't gotten upgraded at the time and it was a friggin nightmare, no lights because the batteries hadn't been checked in the backup lights, sam problem with battery powered IV pumps. No oxygen, hand bagging. Carrying patients down 20-30 flights of stairs. Millions od dead animals rotting -- some that were part of irreproducible experimental research. All subsurface areas flooded and stinking. Radioactive waste lost. Many deaths. Hundreds of millions in diagnostic equipment lost. Horrible, horrible thing.
Major construction at Methodist, St. Lukes, Hermann hospitals, UT and Baylor Med schools to remediate, some of it is not finished yet, over 4 years later. The MEdical center got it really, really badly.