I find it hard to believe that passengers could be on the roof of the monorail for any length of time unless the rescue vehicle extended a bucket all the way up with side rails that "wrapped" over the roof.
There are some points along the monorail route where the train is something like four stories above ground. I think the maximum height for a fire engine ladder truck is five stories. I am sure that some guests would refuse to get off the monorail if all that extended up was an ordinary ladder. They do make ladders (maybe not 5 stories long) that have a tube like grillwork around them for someone to crawl/climb through without danger of falling off the side.