Even for this somewhat moribund forum I'm surprised you haven't gotten a response yet.
I'd guess it's probably one of the R. auriculatum hybrids, such as 'Aladdin', discussed in the 4th paragraph here:
http://www.rosebay.org/chapterweb/spec_aur.htm

Here is a link that might be useful: http://www.rosebay.org/chapterweb/spec_aur.htm

I meant to say Aladdin was another possible hybrid not mentioned on that page. I think it's actually more common in the PNW than several of the ones listed, as I've seen it in Greer's catalog several times.

Here is a link that might be useful: http://vancouver.ca/parks/parks/stanley/pdf/50Rhododendrons.pdf

I noticed it, very pretty as are all his plantings I suspect :)

I didn't comment yet, hadn't wanted to bump it down out of the way before others could view....

And I don't know what it is, but thanks for sharing the photo.