Do you know for sure that it was an ECV owned by the GF/Disney? I know in the past when I have rented ECV's for family members from offiste places, that they are parked in out of the way places until we check-in and pick them up.
That is a good question. I can only tell you that I was told that "they were available to guests who needed them" by a bell serviceman. I cannot tell you if they were in use or reserved or from an outside company, I did not notice any outside vendor stickers on them as I did with others.
I was also told the GF had them available. Because I found out about these I had seen and mentioned on our last day, we were waiting for the Magical Express bus, so I did not get into detailed conversation about them, we were in a bit of a rush.
Its best to check directly with the resorts.