I was driven in a Marriott Bonvoy-decaled Lincoln Navigator from Grosvenor House to Le Royal Meridien in Dubai, despite there being a shuttle service between the two properties, after I checked out of Grosvenor House and was getting ready to check in to Le Royal Meridien.
The St Regis Hong Kong drove me to Hong Kong Station in a very nice Mercedes (not sure if E-Class or S-Class), but I'm not sure if that was actually a hotel car.