As announced in the TfL fares changes decision, from Jan 2nd next year holders of the NR Disabled Railcard will be entitled to discounts at any time when using PAYG on Oyster. This will require a new discount code to be added to the Oyster. ATOC are supposed to be writing to all holders of disabled railcards to tell them about the change, but as yet this doesn’t seem to have happened. We have done some mystery shopping at some Circle line stations and the best answer we got was that it can’t be done until Jan 2nd.
Somewhat alarmingly one station insisted that railcard discounts do not apply to tube travel at all. I’ve passed the results back to TfL so I won’t name and shame just yet.