I've just watched the DVD Cream at Royal Albert Hall 2005 (reunion concerts with Eric Clapton, Jack Bruce, Ginger Baker), the "only supergroup in the 1960s". And what have I seen: Brian sitting in the audience and watching the concert. He seems to be very amused with a big grin on his face and shaking his head. He can be seen on DVD Nr.2 at 3:00min.
Keep on rocking