Sorry if this is old news, but it would seem that you are now able to load your YP railcard onto your oyster, and get 34% off london travelcards & the daily price caps.

Going to go try and do this tomorrow.

Wikipedia says this and apparently there's a few posters advertising it too, tho i'm yet to see them myself.
"As of 2nd January 2008, for people using public transport in London, you can also load the discount onto an Oyster Card at any London Underground ticket office, providing the 34% discount off the cost of a London Travelcard, and the oyster automatic daily cap."