Either you know someone who knows something, or you know someone who is good at making site plans.
Terms like "Existing X" are commonplace on site plans. It gives everyone reading the plan a better idea what they are looking at. Some of the people who will need use the plans may not be familiar with the park, so labeling some squiggly lines as "Existing Batman Roller Coaster" is critical.
The parade route is a critical piece of park infrastructure, complete with narrow gauge rails in the midway. It is more than two yellow lines painted on the ground.
As far as scale goes, there is not really a normal. 1" to 144' such an easy number to work with, 1" to 32', not so much (1" to 36" is much nicer). The part that surprises me is the one inch reference line is sized for normal letter sized paper, rather than large prints. That being said, stuff formatted for letter sized paper is easier for other people to print out to review.
Assuming foundation sizing is being calculated right now, I suspect it is pretty far along in development. I doubt a foundation engineer would be contracted unless the project was green lighted. 2027 is definitely a possibility.