Are you asking if you may bring your own and use it at FW? All the roads and most of the paths are paved, so using an
ECV is easy there. I've met people who've said that they sometimes had to wait for a bus (with lift) that accommodates them but that they enjoyed their ECV there.
If you are asking if FW can provide
ECVs, I don't know. I know you can rent them from area rental businesses for the length of your stay and they will drop them off at your resort and pick them up at the end of the stay.