Was also on that cruise, and yes tendering wasn't possible. Apparently, Disney attempted (unsuccessfully) to negotiate port charges with Monaco for a last minute change on the day and this was the next best option. I'd be surprised if Disney would change itineraries favouring Marseille. The port-city bus literally shows the "rawness" of France's second largest city. We drove past an immigrant camp on the side of the motorway, and some guests didn't even get off the bus, instead deciding to stay onboard and return to the ship. Having said that, as a young couple, we loved the last minute change! We didn't visit the city though, instead we journeyed a half hour away via crowded train to Cassis and saw the Calanques. Too bad Disney didn't come up with an excursion for this last minute, it was the highlight of our trip even with the stress of going it alone.