Wheelchair users do not get to go to the front of lines.
That they do is a common misconception, but it's not true.
People using wheelchairs or ECVs don't get out of waiting in line.
Most of the lines at WDW are wheelchair accessible, so there are very few situations where someone actually goes thru a wheelchair entrance. In most cases, they wait in the same line with everyone else. For a very few attractions, there is an alternate entrace because the regular one isn't accessible and was not able to be made accessible (most in MK or Epcot since they were built before accessibility was thought of). There are some others, where the boarding area is not accessible and wheelchair/
ECV users wait in the regular or Fastpass line and then are pulled into a different area for loading (Buzz Lightyear, Haunted Mansion and Splash Mountain are examples).
AK and the Studio were built with what are called 'Mainstream Lines'. These are lines where the regular line is wheelchair/ECV accessible and a person using a wheelchair or ECV waits in the same line with everyone else.
Here's what it says in the official WDW Guidebook for Guests with Disabilities about Mainstream Lines and the list of attractions with Mainstream Queues:
As you can see, most of the lines are Mainstream Queues:
Magic Kingdom® Park
Ariel's Grotto
Astro Orbiter
Buzz Lightyear's Space Ranger Spin
Donald's Boat
Judge's Tent
Mickey's Country House
Mickey's PhilharMagic
Mike Fink Keelboats (seasonal)
Minnie's Country House
Pirates of the Caribbean
Space Mountain®
Splash Mountain®
Stitch's Great Escape!
The Barnstormer at Goofy's Wiseacres Farm
"The Enchanted Tiki Room Under New Management"
The Hall of Presidents
The Magic Carpets of Aladdin
The Many Adventures of Winnie the Pooh
The Laugh Floor
Tomorrowland® Indy Speedway
Toontown Hall of Fame
Walt Disney's Carousel of Progress (seasonal)
Epcot®
FUTURE WORLD
Imagination!: All Attractions
Innoventions East
Innoventions West
Mission: SPACE
Test Track
The Living Seas: All Attractions
The Land: All Attractions
Universe of Energy: "Ellen's Energy Adventure"
Wonders of Life: All Attractions (seasonal)
WORLD SHOWCASE
China: "Reflections of China"
France: "Impressions de France"
FriendShip Boats
Norway: Maelstrom
The American Adventure: "The American Adventure"
Disney-MGM Studios
Disney-MGM Studios Backlot Tour
Fantasmic!
Lights, Motors, Action! Extreme Stunt Show
Muppet*Vision 3D
Playhouse Disney - Live On Stage!
Rock 'n' Roller Coaster® Starring Aerosmith
Sounds Dangerous - Starring Drew Carey
Star Tours
The Great Movie Ride
The Magic of Disney Animation
"The Twilight Zone Tower of Terror"
Voyage of the Little Mermaid
Walt Disney: One Man's Dream
Disney's Animal Kingdom® Theme Park
Caravan Stage: "Flights of Wonder"
DINOSAUR
Grandmother Willow's Grove: "Pocahontas and Her forest friends"
It's Tough To Be A Bug
Kali River Rapids
Kilimanjaro Safaris
Lion King Theater: "Festival of the Lion King"
Maharajah Jungle Trek
Primeval Whirl
Where's Nemo
The Boneyard
TriceraTop Spin
I wanted to add that Soarin' and EE are missing from the list. They are both Mainstream Access.
And, some attractions have limited number of spots for wheelchairs. We have already shown up for shows where there was still room for ambulatory people, but the wheelchair spots were already filled for that show and we had to wait for the next one (Voyage of the Little Mermaid, where we had Fastpasses; and ITTBAB, where the CMs were practically begging people to come into the queue because there was no wait in the standby line.
There may be an additional wait for someone who needs a wheelchair accessible ride vehicle or if there are already people with disabilities waiting.