Closing this thread as it is no longer sharing useful information.
To summarize what is known.......
Guests with disabilities are expected to wait in line if the current wait time is less than 20 minutes during park hours.
This was/is true for both GAC (discontinued Guest Assistance Card) and
DAS (the current Disability Access Service).
Depending on the attraction, the guest might be directed to either Fastpass line or standby line. (If the wait is less than 20 minutes, the time in line would be fairly similar in both lines).
The great majority of lines during parties are less than 20 minutes.
Party waits are often much less - basically loading as quickly as guests can get from the entrance to the point of loading.
In general, short waits during parties for guests with disabilities are
handled the same during parties as during regular park hours - if the wait is less than 20 minutes, guests using DAS will wait in line.
Many people over the years on this site and other places reported they were not able to use GAC or DAS.
Because of that and the short party waits,
guests with DAS should expect not to be able to use it.
If the posted wait time is 20 minutes or over, and the DAS user wants to go on an attraction - ask the CM at the entrance.
They
may be able to provide accommodation. It will depend on what they have available.
On all the places I follow, a couple of people have reported using DAS during parties, generally for headline attractions that offer Rider Swap.
NOT ALL ATTRACTIONS have Rider Switch. Attractions that offer Rider Switch have more options available and MIGHT handle DAS users similar to Rider Switch.
Many people have reported they were not able to use DAS for party character meet and greets. There may be other opportunities for those, such as having part of your party wait in line and one person wait outside of line with the person with a disability.