Disneyland will still honor past tickets assuming they're not expired. Really amazing of them, and a great way to make someone's day a little brighter without costing them a dime.
This is the first positive news article Disneyland's gotten this summer... hopefully the curse is lifted.
I used a pre-1989 comp ticket back during the 50th. Since it was valid as a park hopper for the Magic Kingdom and EPCOT Center, it was honored as a park hopper at the Disneyland Resort. The actual ticket itself was voided with a small stamp on the back and returned to me to keep as a souvenir.