Oh its absolutely against law to not accommodate handicapped people in any business and stadiums sure as shit can't get away with it.
http://www.steelers.com/tickets-and-stadium/heinz-field-faq.html
More to the point:
Guests with Disabilities
How can I exchange my tickets for handicap accessible seats?
You can go to any guest services kiosk or guest services room. Kiosks are located inside all gates. Guest Services Rooms are located behind section 104, 123, 504, and 528. All exchanges must be done the day of the event.
Once I am inside the stadium, if I need assistance to my seat, what should I do?
Our guest services staff can meet guests at the drop-off locations and take them to their seat via wheelchair. We have wheelchairs available to escort guests from point A to point B. No prior arrangements are necessary. This is a service we provide and it is always in use.
You can go to any guest services kiosk or guest services room. Kiosks are located inside all gates. Guest Services Rooms are located behind sections 104, 123, 504, and 528. The kiosks and the guest services rooms are never left unattended. We can provide directions to your seat, escort someone to their seat via wheelchair, and help with any questions one might have.
We also have 2 courtesy golf cart shuttles. One sits inside of Gate C and one sits inside of Gate B. They run up and down the ramps pre-game only until the ramps are too crowded for them to travel on. They do not run after the games, because of egress. However, we do provide post-game wheelchair escorts as well.
Elevator Questions:
Refer to Club and Suites Section
You may also refer to the Heinz Field Disabilities Guide.